Corporations from AT&T to U.P.S. say business is finally picking up  and investors are cheering.

Robust quarterly results from some of the nation’s bellwether companies galvanized Wall Street on Thursday. Stocks soared in a broad rally that lifted the Dow Jones industrial average more than 200 points.

Big names like AT&T, Caterpillar, U.P.S. and 3M posted surprisingly strong sales and profit figures for the second quarter. Even more encouraging, many also issued upbeat forecasts for the rest of the year, suggesting that, for them at least, a recovery of sorts was at last taking hold.

“It is all about economic and earnings momentum,” Alan M. Gayle, senior investment strategist for RidgeWorth Capital Management, said of the swift response from the markets.

Whether the euphoria will last is uncertain. Quarterly earnings season is now in full swing, and a rush of other results is due over the next week. Disappointments could await. Indeed, after the markets closed Thursday, Amazon.com posted results that missed analysts’ expectations.