At 9.35 am IST, the BSE Sensex was trading down 78 points at 18,129, while the S&P CNX Nifty was trading down 25 points at 5,506.
A spectacular rally in the last few weeks also led to a sluggish opening on Thursday.
Asian indices too were trading in the red, with the Hang Sang, Nikkei and Strait Times all following weak cues from Europe and the US. Shares of Sun Pharma lost 4% after damages were filed against the company on the Protonix patent.
Other heavweights that lost ground in early trade included Reliance Industries, Sterlite Industries and ICICI Bank. On the other hand gainers included Jindal Steel, BHEL and NTPC.