Energy stocks dropped again in the US on Wednesday as oil fell to its lowest price since last summer, extending their dismal start to the year.
Gains for health care and technology stocks helped hem in losses for broader market indexes.
The Standard & Poor's 500 index dipped 1.42 points, or 0.1%, to 2,435.61.
The Dow Jones industrial average fell 57.11, or 0.3%, to 21,410.03, and the Nasdaq composite rose 45.92, or 0.7% to 6,233.95.
"The story truly is energy right now," said JJ Kinahan, chief market strategist at TD Ameritrade.
Crude dropped for a third straight day and touched its lowest price since August on expectations that supplies of oil will far outweigh demand.
Even a report showing that the amount of supplies in U.S. inventories shrank last week did little to alter the tide.
Benchmark US crude lost 98 cents, or 2.3%, to settle at 42.53 dollars per barrel.
Brent crude, the international standard, fell 1.20 dollars, or 2.6%, to 44.82 dollars a barrel.
The price of oil has now dropped more than 20% this year, breaking into what traders call a bear market.
Accelerating corporate profits and expectations that they will continue have been a big reason for the stock market's rise this year, and energy companies had been forecast to provide some of the biggest gains.
"We're in the warning area here, between 40 and 44 dollars," Mr Kinahan said of the price of oil.
"If we get below 40 dollars, I think you'll get people adjusting their expectations."
Energy stocks in the S&P 500 tumbled 1.6%, a day after falling 1.2%.
They are down nearly 15% for the year, when the overall S&P 500 is up 8.8%.
Losses for the broad S&P 500 were milder on Wednesday because of strong gains for health care and technology stocks.
Red Hat, an open-source software company, surged to one of the biggest gains in the index after reporting better-than-expected earnings for its latest quarter.
Its forecast for revenue and earnings this fiscal year also topped analysts' expectations. Its stock rose 8.62 dollars, or 9.6%, to 98.58 dollars.
La-Z-Boy jumped 5.80 dollars, or 22.1%, to 32.00 dollars after reporting quarterly earnings that easily topped analysts' expectations.
Its customers have been shifting toward higher-priced and more profitable products for the company, such as leather.
In overseas markets, the Shanghai composite rose 0.5% after index provider MSCI said it will include 222 of what are called Chinese A-shares in its widely followed Emerging Markets index.
The move, which will begin next year, will likely cause big shifts of money into mainland Chinese stocks by mutual funds and other investors that track the index.
MSCI has been considering including A-shares in its index for years but had demurred until now due to a range of concerns, such as how inaccessible they were for foreign investors.
China has since started a Stock Connect programme that links mainland Chinese stocks with the Hong Kong market to make them more accessible, among other changes.
In Europe, France's CAC 40 fell 0.4%, Germany's Dax lost 0.3% and the FTSE 100 in London slipped 0.3%.
In Asia, Japan's Nikkei 225 index fell 0.5%, South Korea's Kospi lost 0.5% and the Hang Seng in Hong Kong dropped 0.6%.
The 10-year Treasury yield held steady at 2.16%.
The two-year yield dipped to 1.34% from 1.35% late Tuesday, and the 30-year yield fell to 2.73% from 2.74%.
The UK pound rose to 1.2668 from 1.2629 dollars late Tuesday.
The euro rose to 1.1167 from 1.1128 dollars, and the dollar dipped to 111.34 Japanese yen from 111.41 yen.
In the commodities markets, gold rose 2.30 dollars to settle at $1,245.80 per ounce, silver slipped four cents to 16.37 dollars per ounce and copper added five cents to 2.60 dollars per pound. Natural gas fell one cent to 2.89 dollars per 1,000 cubic feet, heating oil fell three cents to 1.36 dollars per gallon and wholesale petrol fell one cent to 1.41 dollars per gallon.