1 William Gates III

$57.0 billion
Source: Microsoft (nasdaq: MSFT - news - people )

Software visionary stepped down from day-to-day duties at Microsoft in June to devote his talents and riches to philanthropy. The $36 billion Bill & Melinda Gates Foundation donates to causes such as fighting hunger in developing countries, improving education in America's high schools and developing vaccines against malaria, tuberculosis and AIDS. Appointed Office veteran Jeffrey Raikes chief exec of Gates Foundation in September. Gates remains Microsoft chairman. Appearing in TV commercials with comedian Jerry Seinfeld as part of campaign to improve Windows brand; Vista operating system continues to get mixed reviews. Sells shares each quarter, redeploys proceeds via investment vehicle Cascade (nyse: CAE - news - people ); more than half of fortune is outside Microsoft. Stock down 5% in past 12 months after failed buyout attempt of Yahoo (nasdaq: YHOO - news - people ) erased 25% pop last fall. Masterful capitalist wants to change the rules. Talked up "creative capitalism" at Davos: "I am an impatient optimist. The world is getting better, but it's not getting better fast enough, and it's not getting better for everyone." Wants companies to match profitmaking with doing good. Inflation-adjusted net worth would top $90 billion if he hadn't given away any cash.

2 Warren Buffett

$50.0 billion
Source: Berkshire Hathaway

Iconic investor crowned the world's richest man in march as Berkshire Hathaway shares ran up 25% between July 2007 and February 2008. Berkshire stock has fallen 15% since, erasing $12 billion from Oracle of Omaha's fortune in 6 months and forcing him to cede the title back to friend and bridge partner Bill Gates. Son of Nebraska politician delivered newspapers as a boy. Filed first tax return at age 13, claiming $35 deduction for bicycle. Studied under value investing guru Benjamin Graham at Columbia. Took over textile firm Berkshire Hathaway 1965. Today holding company invested in insurance (Geico, General Re), jewelry (Borsheim's), utilities (MidAmerican Energy (other-otc: MDPWL.PK - news - people )), food (Dairy Queen, See's Candies). Also has noncontrolling stakes in Anheuser-Busch (nyse: BUD - news - people ), Coca-Cola (nyse: KO - news - people ), Wells Fargo (nyse: WFC - news - people ). Berkshire Hathaway sales in 2007: $118 billion. Issued a challenge to members of The Forbes 400 last October; said he would donate $1 million to charity if the collective group would admit they pay less taxes, as a percentage of income, than their secretaries. Irrevocably earmarked the majority of his Berkshire shares for charity in 2006, mostly to the Bill & Melinda Gates Foundation. Has given $6 billion worth of shares so far.

3 Lawrence Ellison

$27.0 billion
Source: Oracle

Database titan continues to buy up would-be competition; more than 40 acquisitions in the past 4 years. Bought BEA Systems (nasdaq: BEAS - news - people ) for $8.5 billion in January. Revenues up 25% to $22.4 billion this year; profits up 29% to $5.5 billion. Stock down 12% in past 12 months. Invested $125 million in Web software outfit Netsuite; took public in December, stock promptly dropped 30%. His shares still worth $500 million. Chicago native studied physics at U. of Chicago, didn't graduate. Started Oracle in 1977. Public 1986, a day before Microsoft. Owns 453-foot Rising Sun; built a smaller leisure boat because superyacht is hard to park. Squabbling in court with Swiss boating billionaire Ernesto Bertarelli over terms of next America's Cup. Recently unveiled hulking 90-foot trimaran he intends to use to win it.

4 Jim Walton

$23.4 billion
Source: Wal-Mart (nyse: WMT - news - people )

Son of Wal-Mart pioneer Sam Walton (d. 1992) and siblings, sister-in-law reclaim spot in Forbes 400 Top 10 after falling off last year. Wal-Mart shares up 45% since last September, as cash-strapped consumers head to discount-driven superstores in droves. Also profiting from stake in solar-paneling outfit First Solar; shares up 120% in past 12 months. Sam started as J.C. Penney (nyse: JCP - news - people ) clerk in 1940; opened Newport, Ark. five-and-dime store Benjamin Franklin 5 years later. Lost lease in 1950. With brother James started general-store chain in Bentonville, Ark., 1962. Today Wal-Mart is world's largest retailer: 7,300 stores, 2 million employees serve 200 million customers. Sales: $378 billion. Jim chairs Arvest Bank Group, Community Publishers.

5 S Robson Walton

$23.3 billion
Source: Wal-Mart

Son of Wal-Mart pioneer Sam Walton (d. 1992) and siblings, sister-in-law reclaim spot in Forbes 400 Top 10 after falling off last year. Wal-Mart shares up 45% since last September, as cash-strapped consumers head to discount-driven superstores in droves. Also profiting from stake in solar-paneling outfit First Solar; shares up 120% in past 12 months. Sam started as J.C. Penney clerk in 1940; opened Newport, Ark. five-and-dime store Benjamin Franklin 5 years later. Lost lease in 1950. With brother James started general-store chain in Bentonville, Ark., 1962. Today Wal-Mart is world's largest retailer: 7,300 stores, 2 million employees serve 200 million customers. Sales: $378 billion. Rob is Wal-Mart chairman; helping company become eco-friendly through partnership with environmental group Conservation International.

6 Alice Walton

$23.2 billion
Source: Wal-Mart

Daughter of Wal-Mart pioneer Sam Walton (d. 1992) and siblings, sister-in-law reclaim spot in Forbes 400 Top 10 after falling off last year. Wal-Mart shares up 45% since last September, as cash-strapped consumers head to discount-driven superstores in droves. Also profiting from stake in solar-paneling outfit First Solar; shares up 120% in past 12 months. Sam started as J.C. Penney clerk in 1940; opened Newport, Ark. five-and-dime store Benjamin Franklin 5 years later. Lost lease in 1950. With brother James started general-store chain in Bentonville, Ark., 1962. Today Wal-Mart is world's largest retailer: 7,300 stores, 2 million employees serve 200 million customers. Sales: $378 billion. Alice is building Crystal Bridges art museum in Bentonville.

6 Christy Walton & family

$23.2 billion
Source: Wal-Mart inheritance

Daughter-in-law of Wal-Mart pioneer Sam Walton (d. 1992) and siblings reclaim spot in Forbes 400 Top 10 after falling off last year. Wal-Mart shares up 45% since last September, as cash-strapped consumers head to discount-driven superstores in droves. Also profiting from stake in solar-paneling outfit First Solar; shares up 120% in past 12 months. Sam started as J.C. Penney clerk in 1940; opened Newport, Ark. five-and-dime store Benjamin Franklin 5 years later. Lost lease in 1950. With brother James started general-store chain in Bentonville, Ark., 1962. Today Wal-Mart is world's largest retailer: 7,300 stores, 2 million employees serve 200 million customers. Sales: $378 billion. Christy is the widow of John Walton (d. 2005); donated 7-acre San Diego home to Cross Border Philanthropy

8 Michael Bloomberg

$20.0 billion
Source: Bloomberg

Mayor Mike has become America's 8th-richest citizen after a transaction put a solid valuation on Bloomberg LP: he borrowed to buy a 20% stake in his company from Merrill Lynch (nyse: MER - news - people ) in July for $4.5 billion. Today he owns 88% of the financial data and news outfit he founded in 1982. Boston-born son of accountant got engineering degree from Johns Hopkins, M.B.A. from Harvard. Became a trader at Salomon Brothers 1970s, quit with $10 million in stock after merger. Created financial information services firm Innovative Market Systems to sell financial data, analytic tools to Wall Street. Renamed Bloomberg LP 1987; added news service, magazine, cable network, radio station. Spent $74 million to become mayor of New York City in 2001 and $85 million on reelection in 2005. Enjoying 71% approval rating, appears to be looking for ways to do away with term limits as November 2009 election looms. Since last June former Republican no longer affiliated with any political party. Has given away nearly $800 million to charity in the past 5 years; with Bill Gates, planning to invest hundreds of millions to combat smoking worldwide.

9 Charles Koch

$19.0 billion
Source: manufacturing, energy

With brother David, transformed family refining business into America's largest private company. Father, Fred C. Koch (d. 1967), invented method of turning heavy oil into gasoline. Sons Charles, David, Frederick and William inherited Koch Industries after father's death. Charles and David bought out William and Frederick for $1.1 billion in 1983; fraternal fight over deal settled in 2001. Today Koch Industries has stakes in pipelines, refineries, fertilizer, fibers and polymers, forest and consumer products, chemical technology. Brothers each own 42%; collective fortune up $4 billion as oil and fertilizer prices soar. Sales last year: $98 billion. Employs 80,000 workers in 60 countries. Purchased Invista, maker of Lycra and Coolmax fabric, in 2004 for $4.2 billion. Dropped $21 billion on paper and building-supply vendor Georgia-Pacific the following year. Charles studied nuclear and chemical engineering at MIT, chief executive since 1967; cofounder of conservative think tank Cato Institute.

 9 David Koch

$19.0 billion
Source: manufacturing, energy

With brother Charles, transformed family refining business into America's largest private company. Father, Fred C. Koch (d. 1967), invented method of turning heavy oil into gasoline. Sons Charles, David, Frederick and William inherited Koch Industries after father's death. Charles and David bought out William and Frederick for $1.1 billion in 1983; fraternal fight over deal settled in 2001. Today Koch Industries has stakes in pipelines, refineries, fertilizer, fibers and polymers, forest and consumer products, chemical technology. Brothers each own 42%; collective fortune up $4 billion as oil and fertilizer prices soar. David is executive vice president. Sales last year: $98 billion. Employs 80,000 workers in 60 countries. Purchased Invista, maker of Lycra and Coolmax fabric, in 2004 for $4.2 billion. Dropped $21 billion on paper and building-supply vendor Georgia-Pacific the following year. Holds chemical engineering degrees from MIT; pledged $100 million to alma mater for cancer research last year. Pledged another $100 million to New York's Lincoln Center this July.

11 Michael Dell

$17.3 billion
Source: Dell

Computer king returned to chief executive post at his computer outfit last year; stock down 18% since. Plunging margins and higher marketing costs pushed second-quarter profits down 17%. Still believes in PCs; has bought $200 million worth of Dell stock since July. Launched service centers in Wal-Mart to compete with Best Buy (nyse: BBY - news - people )'s Geek Squad. Started business out of U. of Texas dorm room in 1984 with $1,000. Built business with direct-sales method, public 1988. Majority of wealth invested via MSD Capital. Michael & Susan Dell Foundation supports education, health initiatives; endowment exceeds $1 billion.

12 Paul Allen

$16.0 billion
Source: Microsoft, investments

Washington State dropout founded Microsoft with school chum Bill Gates in 1975. Left Microsoft in 1983 after Hodgkin's disease diagnosis. Sold off much of his stake to lose huge sums on far-off visions through holding company Vulcan. Microsoft still makes up 20% of his fortune; shares down 29% since October highs amid botched buyout attempt of Yahoo, worries company can't compete with Google (nasdaq: GOOG - news - people ). Stake in cable outfit Charter Communications (nasdaq: CHTR - news - people ) down 45% since May. Dabbles in odd tech projects; donated $25 million to researchers scanning outer space for signs of intelligent alien life, millions more to create Allen Institute for Brain Science, which maps gene activity in humans and mice. Guitar fanatic owns a rock 'n' roll museum, Jimi Hendrix music rights and artifacts. Also owns football's Seattle Seahawks and basketball's Portland Trailblazers; expanding into pro soccer with Seattle Sounders MLS team in 2009.

13 Sergey Brin

$15.9 billion
Source: Google

The battle for tech dominance continues. Last month the Google Guys took the fight to Microsoft with the launch of Web browser Chrome; attempting to steal some of Internet Explorer's 75% market share. Brin emigrated from Russia. Professor's son met partner Larry Page in computer science Ph.D. program at Stanford. Duo dropped out in 1998 to start Google from friend's garage. Initial financing came from angel investors K. Ram Shriram, Andy von Bechtolsheim, professor David Cheriton; then superstar venture capital firms Kleiner Perkins Caufield & Byers and Sequoia Capital pitched in $25 million. Longtime tech exec Eric Schmidt brought on 2001; took company public 2004. Stock down 40% since alltime highs last November. Sales: $16.6 billion. Net margins: 25%. Brin focuses on Google's technology sector.

14 Larry Page

$15.8 billion
Source: Google

The battle for tech dominance continues. Last month the Google Guys took the fight to Microsoft with the launch of Web browser Chrome; attempting to steal some of Internet Explorer's 75% market share. Professor's son met partner Sergey Brin in computer science Ph.D. program at Stanford. Duo dropped out in 1998 to start Google from friend's garage. Page raised in Michigan. Initial financing came from angel investors K. Ram Shriram, Andy von Bechtolsheim, professor David Cheriton; then superstar venture capital firms Kleiner Perkins Caufield & Byers and Sequoia Capital pitched in $25 million. Longtime tech exec Eric Schmidt brought on 2001; took company public 2004. Stock down 40% since alltime highs last November. Sales: $16.6 billion. Net margins: 25%. Page heads Google's product division.

15 Sheldon Adelson

$15.0 billion
Source: casinos, hotels

Rough year for Sin City's richest man. America's 3rd-richest man last year has seen fortune dwindle by $13 billion; shares of his Las Vegas Sands (nyse: LVS - news - people ) casino company have fallen 65% since last October as gamblers stay home, Wall Street falls out of love with Macau. Cabdriver's son borrowed $200 from uncle to sell newspapers at age 12. Created computer industry's marquee event, Comdex, mid-1980s; sold show to Japan's Softbank for $862 million 1995. Built $1.5 billion all-suites Venetian Resort Hotel Casino and the 1.2-million-square-foot Sands Convention Center 1997. Enticed conventioneers to Sin City midweek, took emphasis off gambling. In January opened $1.9 billion Palazzo resort next to nemesis Steve Wynn's Wynn Las Vegas. Unveiled $2.4 billion Venetian Macau in China last August; 10.5-million-square-foot mega-resort features 3,400 slots, 800 tables, 3,000 suites and a convention center. Owns Israeli newspaper Israel Today.

15 Steven Ballmer

$15.0 billion
Source: Microsoft

Microsoft chief attempted to take over Yahoo for $44.6 billion in February; attempt to compete with Google on search backfired after 6-month slugfest—featuring nasty Carl Icahn proxy fight—yielded no deal, sluggish stock price. Worse: Yahoo struck ad deal with Google soon after. Gaining some traction in online advertising; ranked first in display ads this June. Sales up 18% to $60 billion in 2007; net profits rose 26%. Entertainment division—videogame console Xbox, music player Zune—finally profitable. Detroit native dropped out of Stanford M.B.A. program to join former Harvard classmate Bill Gates in 1980.

15 Abigail Johnson

$15.0 billion
Source: Fidelity

With family, runs Fidelity Investments, America's largest mutual fund company. Assets under management: $1.5 trillion. Father Edward III joined company as analyst 1957, president 15 years later. Abby ran her first diversified fund 1993. Ned reduced his ownership in 1995, Abby inherited a 24% stake; she is rumored to have sold shares back to family in recent years. Individual stakes now a secret. Family owns 49% of company. Abby became president of company's mutual fund division 2001. Today runs Personal & Workplace Investing division. Last year several top executives resigned, fueling speculation that Abby will eventually take over from Ned.

18 Jack Taylor & family

$14.0 billion
Source: Enterprise Rent-A-Car

Left Washington U. to join Navy; served as a fighter pilot on U.S.S. Enterprise during WWII. Became sales manager for St. Louis Cadillac distributor. Took 50% pay cut to start company that provided replacement cars; eventually rented cars to customers with stolen or damaged vehicles. Business took off 1970s when insurance companies were ordered by courts to pay for replacement rentals. Today Enterprise Rent-A-Car revenues exceed $9 billion. Rental car business lagging as automakers sell fleets fewer cars at higher prices. Enterprise skirting industry woes by focusing on insurance replacements; demand remains steady so long as cars break down. Appointed nonrelated exec Pamela M. Nicholson president; son Andrew is chief executive; daughter Jo Ann Taylor Kindle runs Enterprise Foundation. Offering hybrid rentals; created Enterprise Rent-A-Car Institute for Renewable Fuels.

19 Anne Cox Chambers

$13.0 billion
Source: Cox Enterprises

Surviving daughter of Cox Enterprises founder James M. Cox (d. 1957); sister Barbara Cox Anthony passed away in 2007. James Sr. worked as a newspaper reporter before buying Dayton Evening News for $26,000 in 1898. Segued into politics; 3-term Ohio governor. Today media empire includes nation's third largest cable television company, 17 daily newspapers, 15 TV stations, 86 radio stations, used car retailer Manheim Auctions, Cox Auto Trader. Sales exceed $15 billion. Nephew James Kennedy runs operation.

20 Donald Bren

$12.0 billion
Source: real estate

Son of Hollywood producer attended U. of Washington on skiing scholarship; halted Olympics bid after injury 1956. Joined Marines, then built first house on $10,000 loan 1958. Developed 10,000-acre Rancho Mission Viejo in California, sold to Philip Morris 1967. With partners, bought real estate developer Irvine Co. for $337 million 1977. Became firm's sole owner in 1996. Developed central Orange County, Irvine and half of Newport Beach. Today owns 9,000 developable acres in Orange County, 400 office buildings, 40 retail centers, 90 apartment communities, hotels, marinas, golf courses. Paid $1.4 billion last October for 90% stake in 16 apartment complexes owned by Archstone-Smith. Republican donor actively involved in McCain's presidential bid. Gave $20 million to UC, Irvine's law school last August, another $8.5 million to California afterschool program for low-income students this year.

20 Carl Icahn

$12.0 billion
Source: leveraged buyouts

Another year, another slew of proxy battles for The Forbes 400's richest "shareholder activist." Appeased in August by Jerry Yang, got 3 seats on Yahoo's board after pushing the sluggish search outfit all summer to take $44.6 billion buyout offer from Microsoft. Bane of corporate ineptitude may be losing his touch; shares of holding company Icahn Enterprises (real estate, hedge funds) down 60% since January. Started Wall Street career in securities arbitrage at Dreyfus & Co. Big money in 1980s buyouts. Publishes blog about "anti-Darwinian" executives, "myth" of corporate democracy.

20 George Kaiser

$12.0 billion
Source: oil & gas, banking

Family fled Nazi Germany 1938, settled in Oklahoma. Parents developed oil and gas business. Took over 1969. Today Kaiser-Francis Oil among the biggest private energy producers. Diversified: owns $1.9 billion stake in Bank of Oklahoma, vast private equity holdings, large derivatives and energy trading portfolio. Sold half of liquefied natural gas outfit Excelerate Energy this year after buying more than $1 billion worth of gas tankers. Passionate philanthropist fights childhood poverty through George Kaiser Family Foundation; helping to develop blighted stretch of Arkansas River. Says billionaire Tom Ward : "He's one of the most generous and charitable men in the world.

درێژه‌ی باسه‌که‌