The Bombay Stock Exchange benchmark Sensex rose by 181 points in the opening trade today, taking a firm trend in overseas markets.The Sensex was trading at 18,106, up by over 120 points when reports last came in. The wide-based National Stock Exchange index Nifty surged 52 points to 5,453 points in the opening trade.Meanwhile, Hong Kong's Hang Seng Index rose 1.03 per cent and Japan's Nikkei index was trading higher by 2.65 percent in early trade today. The Dow Jones Industrial Average index rose 1.44 per cent on Tuesday's trade.