The 30-share barometer declined by 50.84 points, or 0.25 per cent, to 20,162.12. The index had gained 521.29 points in the previous two sessions.
Stocks of metal, capital goods, auto, IT and banking sectors were major losers largely on profit-booking.
Similarly, the wide-based National Stock Exchange index Nifty fell by 18.50 points, or 0.30 per cent, to 6,128.25.
Brokers said selling, mostly of a profit-booking nature, by funds after two sessions of gains amid a mixed trend on other Asian bourses, mainly influenced the trading sentiment here.
The US Dow Jones Industrial Average gained 0.40 per cent to close at new all-time in yesterday's trade.