The shuttle carried a crew of four – the largest spacecraft crew up to that time – and the first two commercial communications satellites to be flown aboard a shuttle.

The commercial satellites were deployed successfully and subsequently propelled into their operational geosynchronous orbits by McDonnell Douglas PAM-D kickmotors. The two satellites were SBS 3, owned by Satellite Business Systems, and Anik C3, owned by Telesat Canada; both were Hughes-built HS-376-series satellites. In addition, STS-5 carried a West German-sponsored microgravity GAS experiment canister in the payload bay. The crew also conducted three student-designed experiments during the flight.

A planned spacewalk by Lenoir and Allen, the first of the Space Shuttle program, was postponed by one day after Lenoir became ill, and then had to be cancelled when the two spacesuits that were to be used developed problems.