The 30-share BSE barometer, which had climbed to 18,735.95 points in early trade, fell by 52.67 points, or 0.28 per cent, to settle at 18,579.50 points.
The broad-based Nifty of the National Stock Exchange fell by 13.95 points, or 0.25 per cent to 5,649.50, after touching the day's high of 5,693.70.
Brokers said investors squared up their pending positions following monthly expiry in the derivatives segment.
They said selling pressure was so strong that a better trend in global markets failed to check the falling trend.
Reliance Industries dropped by 1.65 per cent to Rs 830.20 and Infosys by 1.47 per cent to Rs 2,548.70. The two scrips carry nearly 18 per cent weightage on the benchmark.
IT stocks were down due to concerns over demand outlook from global markets and the recent rally in the rupee. These companies get over 50 per cent revenue from the US and European markets.
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Among 30-BSE index components, 19 stocks fell.
Stocks of refinery, information technology and metal sectors suffered heavy losses.
Bucking the general weak trend, stocks of fast moving consumer goods and capital goods ended with gains. ITC rose by 1.25 per cent to Rs 266.50 and Hindustan Unilever by 1.59 per cent to Rs 536.15.