Apple briefly surpassed Exxon Mobil as the most valuable company in the U.S. Tuesday afternoon before settling back slightly lower.
But the two are now so close that the change of guard is likely to happen soon.
Apple Inc.'s stock gained 5.9 percent to $374.01 on Tuesday, bringing the iPhone and iPad maker's market capitalization to about $347 billion when the market closed.
Exxon Mobil Corp. shares, meanwhile, closed up 2.1 percent at 71.64. That gives the oil company a market cap of $348 billion as of the market's close.
Other big-name corporations, such as Wal-Mart Stores Inc. and General Electric Co., don't even come close. Apple overtook Microsoft, the previous No. 2, just last year.