THE 500 largest US companies scored near-record profits last year and retailer Wal-Mart replaced ExxonMobil as the biggest revenue maker on the annual list, Fortune magazine says.
Apple cracked into the top 10 companies for the first time, vaulting into sixth place from the prior year's number 17 slot.
The combined earnings of the Fortune 500 came in at $US820 billion ($798.87 billion) in 2012, slipping from the all-time high of $US824.5 billion in 2011.
Earnings amounted to 6.8 per cent of sales, well above the historical average of around 5.5 per cent, the magazine said.
"For the future the overriding question for the 500 is whether the era of abundant profits will continue," said Fortune senior editor-at-large Shawn Tully.
Mr Tully predicted that companies would be forced to increase their staff and pay higher salaries as the economy continues to improve.
"Most likely that will hold profit growth to the low single digits in the next year or two, in line with sales, as gravitational forces pull earnings back to the mean."
Mr Tully characterised 2012 as a year that saw the return of "animal spirits" or an urge to action, reflected in an increase in the number of spinoffs and mergers and acquisitions.
"For several years, players have been hoarding cash and shunning expansion," Mr Tully said. "In 2012 they put that cash - and their rapidly appreciating shares - to work in the best year for M&A in over a decade."
Wal-Mart reclaimed the top spot on the list from energy titan ExxonMobil after posting $US469.2 billion in revenues, or $US19.3 billion more than Exxon.
However, Exxon's profits of $US44.9 billion dwarfed the retailer's $US17.0 billion.
Exxon and Wal-Mart have traded the top two positions repeatedly in recent years. This year marks the ninth time Wal-Mart has topped the list.
Energy companies continued to play a prominent role in the group, with Chevron in third place and refiners Phillips 66 and Valero Energy placing fourth and ninth, respectively.
Rounding out the rest of the top 10 were Warren Buffett's Berkshire Hathaway, ranked in fifth place, Apple (six), General Motors (seven), General Electric (eight) and Ford Motor (10).
The magazine classified financial services as the "comeback" sector of the year, leading all industry groups with $US200 billion in total profits, ahead of the technology sector.
JPMorgan Chase ranked 18th, Bank of America placed 21st, Wells Fargo was 25th and Citigroup finished 26th.
