Shares rose for Caterpillar, the world's largest construction and mining equipment company, gaining 48 cents to $84.34. But the company warned that it expects lower profit and revenue for the rest of the year.
And the reports on Monday followed other dissatisfying results last week from companies like Microsoft, General Electric and McDonald's.
To be fair, most companies are reporting better-than-expected profits. But now, investors want to know how companies are faring on revenue. Revenue can give a more accurate picture of how a company is performing, because profits can vary widely on items like accounting charges and cost-cutting.
David Katz, principal and senior portfolio strategist at WeiserMazars Wealth Advisors in New York, described companies' third-quarter revenue results as "fair" and said the U.S. economy is "slow and steady."
"It is at a snail's pace," he said. "But it's certainly better than what we had."
Of the roughly 100 companies in the S&P 500 that had reported third-quarter results as of Friday, 70 percent have beat analysts' estimates for profits, according to John Butters, senior earnings analyst at FactSet. But only 42 percent have beat estimates for revenue. That's the lowest since the first quarter of 2009, when the stock market hit its Great Recession lows.
Company profits so far this quarter are down 2.3 percent compared to a year ago. Revenue is down 0.6 percent.
One stock that jumped was Ancestry.com, the genealogy website, which announced it will be bought by European private equity firms. The stock popped $2.28 to $31.46. The buyers had offered $32 per share.
In other trading, the yield on the 10-year Treasury note rose to 1.79 percent from 1.76 percent late Friday. The euro was worth $1.30, little changed from Friday, and energy prices fell slightly. Crude oil fell $1.11 to $89.33 a barrel in New York.