Off-spinner Ravichandran Ashwin claimed a five-wicket haul as India secured a 142-run lead at stumps after bundling out South Africa for 184 on the second day of the opening Test in Mohali on Friday.
In response to India's first innings score of 201, South African batsmen failed to counter the spin challenge from the opposition despite stiff resistance from AB de Villiers (63) and captain Hashim Amla (43).
Ashwin was ably supported by Ravindra Jadeja as he bagged three wickets while Amit Mishra chipped in with two wickets.
At the close of play, India made 125 for two wickets, with Cheteshwar Pujara and skipper Virat Kohli remaining at the crease on their respective scores of 63 and 11.
Earlier, Shikhar Dhawan was dismissed on his second consecutive duck before Murali Vijay fell on a delivery by Imran Tahir for 47.
After losing limited-overs series, India are aiming to bounce back and salvage pride in the first of the four-match Test series.