Technology stocks have been volatile since Election Day, with some industry leaders expressing concern that President-elect Donald Trump's protectionist policies could harm the sector.
Analysts said Wednesday's drop reflected a rotation from technology to other sectors expected to benefit from Trump. Amazon, Facebook and Google parent Alphabet all lost 1.5 percent or more.
Biotechnology stocks were another weak area, with Celgene losing 3.0 percent and Gilead Sciences 1.5 percent.
The tech-rich Nasdaq Composite Index ended down 1.1 percent to 5,323.68.
The Dow Jones Industrial Average added just two points, less than 0.1 percent, to close at 19,123.58, while the broad-based S&P 500 lost 0.3 percent to 2,198.81.
"The stock market closed a strong month on a sloppy note," Briefing.com said.
"Equity indices entered the day with an assortment of positive headlines to rally behind, but what we saw instead, was a continuation of the selling that showed up during the last hour of yesterday's session."
Chevron rose 2.0 percent, while Halliburton surged 11.1 percent and Marathon Oil 20.8 percent after an OPEC deal to cut production boosted oil prices.
Dow members JPMorgan Chase and Goldman Sachs added 1.6 percent and 3.6 percent, respectively, in anticipation of favorable policies from the incoming Trump administration.
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