The 30-share index, which had gained 173.65 points yesterday, fell by 65.90 points, or 0.35 per cent, to 18,738.85 with stocks of IT, capital goods and power sectors leading the fall in first five minutes of trade.
Similarly, the wide-based National Stock Exchange index Nifty declined by 13.20 points, or 0.23 per cent, to 5,694.85.
Selling pressure sparked after below-market-expectations September quarter earnings by IT major Infosys, mainly influenced the trading sentiment, brokers said.
Funds and retail investors booking profits at prevailing higher levels also aided the fall in Sensex.
However, better trend in the Asian region restricted the loss, they added.
Shares of Infosys fell by 7.10 per cent to Rs 2,351.60 in early trade, after the company reported consolidated profit for July-September period at Rs 2,369 crore, a growth of 24.29 per cent.
In the Asian region, Hong Kong's Hang Seng index was up by 1.07 per cent, while Japan's Nikkei Index gained 0.71 per cent in the morning trade today.
