The 1978 USAC Championship Car season consisted of 18 races, beginning at Phoenix on March 18 and concluding at the same location on October 28.

The USAC National Champion was Tom Sneva and the Indianapolis 500 winner was Al Unser.

By winning the Indianapolis 500, Pocono 500, and California 500, Al Unser swept the Indy car "Triple Crown", the only driver in history to do so.

Sneva's "winless" championship was not without its critics, however, a statistician calculated points results using contemporary points tables from other major racing series, and concluded that Sneva would have still won the title in nearly every scenario.

Mario Andretti was running the full Formula One season (of which he would be World Champion).