The Sensex at the Bombay Stock Exchange fell 75 points, or 0.4 per cent, to 18,684 in opening trade, today, on profit-booking by investors, amid weakness in the other Asian bourses. Later, the Sensex lost further ground, and stood 124 points, or 0.7 per cent in the red, at 18,634 in afternoon trade, a short while ago.Stock markets in Japan, China, Hong Kong, Taiwan and South Korea had lost between 0.8 percent and 1.7 percent today. The US Dow Jones Industrial Average had ended 0.2 per cent higher in yesterday's trade.