The BSE benchmark Sensex today fell by nearly 51 points in early trade as funds and retailinvestors booked profits after recent gains, amid a mixed trend in other Asian markets. The 30-share barometer declined by 51 points to 20,162. The index had gained 521 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 to 6,128.25.In the Asian region, Japan's Nikkei Index was down 1.42 per cent, while Hong Kong's Hang Seng index up 0.31 per cent in early trade. The US Dow Jones Industrial Average gained 0.40 per cent to close at new all-time in yesterday's trade.