Apple, Microsoft and Amazon, the most valuable companies on the market, sustained some of the worst losses.
After a brutal October, stocks had started to recover early this month. But continued losses for tech companies have sent major indexes lower again.
The S&P 500 index fell 45.54 points, or 1.7 percent, to 2,690.73. The Dow Jones Industrial Average sank 395.78 points, or 1.6 percent, to 25,017.44. It was down as much as 512 earlier.
The Nasdaq composite skidded 219.40 points, or 3 percent, to 7,028.48. The Russell 2000 index of smaller-company stocks lost 30.99 points, or 2 percent, to 1,496.54.
Investors focused again on trade tensions between the U.S. and China after they clashed at a Pacific Rim summit over the weekend.
A steep loss for Boeing, a major exporter which would stand to suffer greatly in a protracted trade war, weighed heavily on the Dow. Boeing gave up 4.5 percent to $320.94, but is still one of the best-performing stocks in the 30-stock index. Apple fell 4 percent to $185.86 on renewed worries that iPhone sales could slow, Microsoft lost 3.4 percent to $104.62 and Amazon gave back 5.1 percent to close at $1,512.29.
High-dividend stocks like real estate companies and utilities, which investors favor when they are fearful of market turmoil, held up better than the rest of the market.
Among tech and internet stocks, chipmaker Nvidia dropped another 21 percent to $144.70. Nvidia said last week that it had a large number of unsold chips because of a big drop in mining of cryptocurrencies. Facebook sank 5.7 percent to $131.55 and Netflix lost 5.6 percent to $270.21.
The S&P 500 index of technology companies has now plunged 13.1 percent since the end of September.
Industrial companies and retailers also stumbled. Caterpillar fell 3.1 percent to $125.98 and Nike lost 3 percent to $72.52.
Benchmark U.S. crude reversed an early loss and rose 0.5 percent to $56.76 a barrel in New York. U.S. crude prices have dropped for six weeks in a row and are trading around their lowest level in about nine months.
Brent crude, used to price international oils, was little changed at $66.79 a barrel in London.
Wholesale gasoline added 0.4 percent to $1.58 a gallon. Heating oil gained 0.6 percent to $2.09 a gallon. Natural gas surged 10 percent to $4.70 per 1,000 cubic feet.
The parent company of California utility Pacific Gas & Electric fell again after it disclosed that it had a power line failure near the start of a deadly wildfire the morning the fire began. The Camp Fire has killed at least 77 people and destroyed more than 10,500 homes.
PG&E stock fell 4.7 percent to $23.26. The stock has plunged 51 percent since Nov. 8.
Gold rose 0.2 percent to $1,225.30 an ounce. Silver inched up 0.1 percent to $14.40 an ounce. Copper held steady at $2.80 a pound.
Bond prices rose. The yield on the 10-year Treasury note fell to 3.05 percent from 3.07 percent. The dollar slipped to 112.54 yen from 112.83 yen. The euro rose to $1.1453 from $1.1412. The pound rose to $1.2855 from $1.2831.