Facebook, Google and Netflix — all big winners over the past year — fell sharply, contributing to a rout in the technology sector. Biotech companies, another recent favourite, also took a beating.
The tech-heavy Nasdaq composite plunged 110 points, or 2.6 per cent, to 4,127, its biggest drop in two months.
Other major indexes fell, but not nearly as much.
The S&P 500 index fell 23 points, or 1.3 per cent, to 1,865. The index traded at an all-time high earlier in the day.
The Dow Jones industrial average lost 159 points, or 1 per cent, to 16,412.
As traders dumped tech stocks, they shifted money into less volatile companies like Coca-Cola, Johnson & Johnson and utility stocks.