The domestic stock markets started Tuesday's session on a flat note, with a negative bias. The S&P BSE Sensex started at 35,394.77 against its last close of 35,354.08 and the Nifty50 barometer of the National Stock Exchange (NSE) opened at 10,621.45 against its previous close of 10,628.60. However, at 9:18 am, the 30-share Sensex traded at 35,370.14, up 16.06 points or 0.05 per cent and the 50-scrip Nifty was at 10,632.40, with a gain of 3.80 points or 0.04 per cent.