The 30-share index, which shed 1.34 points in the previous session, drifted by 77.67 points, or 0.45 per cent to 17,088.95 points in the opening trade.
The wide-based National Stock Exchange index Nifty also declined by 34.80 points, or 0.67 per cent to 5,102.20 points.
Brokers said weakening trend on the Asian stock markets mainly dampened the trading sentiments here, triggering selling by foreign funds.
Besides, profit-booking by retail investors as Sensex has has gone up by nearly 8 per cent in just over one month also led to fall in stock prices, they added.
Among losers were Reliance Industries down 0.26 per cent to Rs 1,018.55, Infosys Technologies 1.11 per cent to Rs 2,643, Tata Consultancy Services 0.21 per cent to Rs 795.10, ICICI Bank 1.14 per cent to Rs 926.20, State Bank of India 0.81 per cent to Rs 2,029 and Sterlite Industries 0.47 per cent to Rs 824.
Meanwhile, Hong Kong's Hang Seng index was down 0.88 per cent, while Japan's Nikkei was down 0.20 per cent in the morning trade today.
