The Sensex at the Bombay Stock Exchange remained slightly weak in afternoon trade, and stood 38 points, or 0.2 percent in negative territory, at 20,860 a short while ago. Earlier in the morning, the Sensex had fallen 49 points, or 0.2 per cent, to 20,849, as investors booked profits after recent gains. The 30-share Sensex had rallied 478 points in the previous three trading sessions. Stock markets in Japan, China, Indonesia, Hong Kong, Taiwan, South Korea and Singapore were trading mixed, today. The US Dow Jones Industrial Average had ended 0.5 per cent lower in yesterday's trade.