The Bombay Stock Exchange benchmark Sensex gained over 137 points in opening trade on the last day of the 2010-11 financial year. It was trading at 19473, up by over 183 points a short while ago. Brokers said overnight gains in the US market and a firm trend on Asian bourses buoyed the trading sentiment in domestic markets. Meanwhile, Hong Kong's Hang Seng index was up marginally by 0.07 per cent in early trade on Thursday. The US Dow Jones Industrial average ended 0.58 per cent higher in the previous session.