Smith set the 100 metre world record on July 3, 1983 at the U.S. Olympic Festival at Colorado Springs, with a run of 9.93 seconds.

At the 1984 Summer Olympics in Los Angeles, Smith became champion as part of the U.S. 4x100-meters relay team, again establishing a new world record in this event.

Smith missed out on what seemed like a likely win in the 4x100-meters relay in Seoul because the U.S. team did not reach the final following a disqualification for passing the baton outside the legal area.

In the later years of his career, he was named captain of the U.S. track and field team at major events including the Olympic Games and World Championships.

Ben Johnson of Canada crossed the line first, with Lewis second, Linford Christie of Great Britain third, and Smith fourth.

Johnson was not the only participant whose success was questioned: Lewis had tested positive at the Olympic Trials for pseudoephedrine, ephedrine and phenylpropanolamine.

[2] Fellow Santa Monica Track Club teammates Joe DeLoach and Floyd Heard were also found to have the same banned stimulants in their systems, and were cleared to compete for the same reason.

Smith was ranked among the best in the USA and the world in both the 100 and 200 m sprint events from 1980 to 1993, according to the votes of the experts of Track and Field News.