Benchmark indices opened on a positive note on Thursday, led by buying in stocks such as Reliance Industries, ICICI Bank, Tata Motors and SBI. At 9.21 am, the Sensex was trading 181.48 points, or 0.55 per cent, higher at 33,400.29. The Nifty50 was trading at 10,364.90, up 61.75 points, or 0.60 per cent.