Between March 1985 and December 1989, 86 patients underwent heart (80) or heart-lung (6) transplantation. Thirty-seven (43%) developed one or more significant gastrointestinal problems. Dyspepsia and gallbladder disease were common, but easily managed. Cytomegalovirus disease occurred in 25 patients (29%) and required aggressive investigation and early therapy with ganciclovir; all patients so treated responded satisfactorily. Features of acute peritonitis were seen in 6 patients and required exploratory laparotomy in 4. Non-Hodgkin's lymphoma of the stomach in one patient has regressed following a combination of reduction in immunosuppressive therapy and a course of chemotherapy. The development of hepatitis or severe liver dysfunction of unknown cause has been associated with significant morbidity and mortality. Since this study was undertaken, the incidence of gastrointestinal complications has been greatly reduced by modifications to our immunosuppressive and anti-infection prophylactic drug protocols. Nevertheless, such complications still occur and it is important that the gastroenterologist should understand the need for urgent and intensive investigation and therapy.