The 30-share barometer, which had gained nearly 299 points in the previous three sessions, declined by 19.89 points, or 0.10 per cent, to 20,129.96.
Stocks of oil and gas, power and realty sectors were the major losers due to profit- booking.
Similarly, the wide-based National Stock Exchange index, Nifty, moved down by 7.90 points, or 0,13 per cent, to 6,021.13.
Brokers said profit-booking by funds and retail investors after three sessions of gains mainly influenced the trading sentiment.
In the Asian region, Japan's Nikkei Index rose by 1.23 per cent, while Hong Kong's Hang Seng index by by 0.64 per cent in early trade today.