The gastrointestinal manifestations of drug-induced immunosuppression may result from direct drug effects, from infectious complications, or both. Graft-versus-host disease (GVHD) is a third mechanism whereby immunosuppressive agents are linked with gastrointestinal injury. This article reviews individual immuno-suppressive medications, first concentrating on their reported gastrointestinal side effects, then reviewing other gastrointestinal phenomena, which may represent side effects of immunosuppressive agents but have not been reported yet.