FORTUNE 500

1. Wal-Mart Stores
Fortune 500 rank: 1 (Previous rank: 2)
2006 Revenues (millions): $351,139
Headquarters: Bentonville, AR
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The retail giant reclaims the top spot on the Fortune 500, making it the largest company in the United States for the fifth time in six years. The company suffered a series of public relations gaffes last year, but has launched a crusade to spruce up its image. It now employs 1.9 million people worldwide and revenues are up 11% over last year, but profits grew less than 1%, amid a slowdown in same-store sales.

2. Exxon Mobil
Fortune 500 rank: 2 (Previous rank: 1)
2006 Revenues (millions): $347,254
Headquarters: Irving, TX
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Though it's not No. 1 this year, the oil giant remains the most profitable company in the Fortune 500, with $39.5 billion in 2006 earnings, thanks to record crude oil prices in 2006. Revenues are up 2% over last year. Profits jumped 9%. The outfit is a leader in energy exploration, with projects in Africa, Russia and the Persian Gulf.

3. General Motors
Fortune 500 rank: 3 (Previous rank: 3)
2006 Revenues (millions): $207,349
Headquarters: Detroit, MI
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In a year that saw GM sell a majority stake in its most profitable unit, GMAC, and had tens of thousands of factory workers take large payouts to leave the company, the world's largest automaker made progress in its turn-around efforts. Still, the company posted a $2 billion net loss, and has yet to break even in its core North American auto operations.

4. Chevron
Fortune 500 rank: 4 (Previous rank: 4)
2006 Revenues (millions): $200,567
Headquarters: San Ramon, CA
Get quote: CVX

Chevron's merger with Unocal was finalized in 2006, helping to give the oil giant a banner year, with $17.1 billion in earnings. Chevron boosted its reserves by 950 million barrels, and results were also helped by new oil production in Angola. Revenues are up 6% over last year. Profits jumped 22%.

5. ConocoPhillips
Fortune 500 rank: 5 (Previous rank: 6)
2006 Revenues (millions): $172,451
Headquarters: Houston, TX
Get quote: COP

The company managed to boost profits by 15%, to $15.5 billion, on only 4% revenue growth. But with corroded pipes and bad weather disrupting production and transportation at its drilling operations in Alaska, the company struggled to replenish reserves. Of the 2.5 billion barrels that it added, all but 100 million of them were from acquisitions.