The S&P 500 hit a new intraday record Friday but stocks then pulled back ahead of the weekend amid profit taking and caution over the Ukraine crisis.
The Dow Jones Industrial Average finished down 28.28 points (0.17 percent) at 16,302.77.
The broad-based S&P 500 lost 5.49 (0.29 percent) at 1,866.52, while the tech-rich Nasdaq Composite slid 42.50 (0.98 percent) to 4,276.79.
Earlier the S&P 500 pushed to a new record at 1,883.97, but could not hold on to the gains. Sellers hit tech stocks in particular, and banks which had been strong in early trade also pulled back.
After a bumpy week marked by rising tensions between Russia and the West over Ukraine, and the Federal Reserve stirring the markets with confusing signals on interest rates, "it was not surprising that we had some profit taking," said Mace Blicksilver of Marblehead Asset Management.
He said the expiration date of options also distorted the market, adding some volatility.
The profit taking could be seen in the sell-off of leading tech shares: Oracle (-2.3 percent), Amazon (-2.3 percent), Tesla (-2.6 percent) and Netflix (-4.3 percent).
Biotech also took a hit with Gilead Sciences (-4.8 percent) and Biogen Idect (-8.2 percent).
Apple (+0.8 percent) and Facebook (+0.4 percent) stood out among a handful of gainers among the Nasdaq's largest companies.
On the Dow, Johnson & Johnson led gainers, up 1.9 percent, followed by Caterpillar, up 1.2 percent.
Nike sank 5.1 percent after warning that sales of its popular sports clothing in major emerging markets could be weak.
IT security company Symantec plunged 12.9 percent after the company sacked its chief executive, Steve Bennett, who took the fall for slumping sales and a share price which has shed 24 percent over the past 12 months.
Bond prices climbed. The yield on the 10-year US Treasury fell to 2.74 percent from 2.78 Thursday, while the 30-year dropped to 3.61 percent from 3.66 percent. Bond prices and yields move inversely.