The BSE benchmark Sensex today gained almost 36 points in early trade on fresh buying by funds and retailers ahead of industrial output data, amid a firmingtrend on other Asian bourses. The 30-share barometer, which had lost 37 points yesterday, recovered by 36 points, or 0.18 per cent, to 19,681, led by gains in oil and gas, auto and realty sector stocks. Similarly, the wide-based National Stock Exchange index Nifty moved up by 2 points, or 0.04 per cent, to 5,944.