After climbing to 20,086.43 at the outset, the BSE benchmark was hit hard by profit-booking as costlier onion and other vegetables pushed up inflation for the third month in a row to 6.1 per cent in August.
The Sensex finally closed at 19,742.47, up just 9.71 points, or 0.05 per cent compared to Friday's closing value.
Traders said besides dashed rate cut hopes, concerns that the central bank may not wind down its liquidity-tightening measures also was a factor in investors selling off positions.
Brokers said selling pressure remained strong enough and domestic markets ignored a firming trend in the Asian region as well as a higher opening in Europe.
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While banking, auto, FMCG and public sector undertaking stocks clocked gains, drop in Reliance Industries, Infosys and TCS dragged down the 30-share index.
In banking, ICICI and HDFC notched up good gains. ITC, Bharti Airtel and ONGC also rose.
Global stocks rose on reports that former US Treasury Secretary Lawrence Summers, who was said to be in the race to replace Fed Chairman Ben Bernanke in January next year, has pulled out of the race for the top job.