He won two medals at the 1987 World Championships in Rome. Recording 10.08 s, he won the bronze medal in the 100 m, behind Ben Johnson and Carl Lewis; his finish position and medal were later upgraded after Johnson was disqualified following his positive test for a steroid at the 1988 Olympics and later admission of seven years of use. Running the anchor leg for the 4 × 100 m relay team he earned a bronze medal in 38.41 s. Stewart finished the season ranked number four in the world.