Cytomegalovirus (CMV) causes major morbidity in organ transplant recipients. Gastrointestinal disease was the most prominent manifestation of CMV infection in a population of heart and heart-lung transplant patients, with an incidence of 9.9%, compared with pneumonitis (4.0%) and retinitis (0%), and occurred most frequently in CMV-seronegative recipients of organs from CMV-seropositive donors. Clinical manifestations included gastritis (nine patients), gastric ulceration (four patients), duodenitis (three patients), esophagitis (one patient), pyloric perforation (one patient), and colonic hemorrhage (one patient). Patients with gastrointestinal CMV infection were treated with intravenous ganciclovir sodium therapy, 5 mg/kg twice daily, for 2 to 8 weeks, with positive clinical, endoscopic, histologic, and virologic responses. Relapses occurred in four of nine patients who were followed up for a median period of 18 months. Retreatment resulted in healing of endoscopic lesions and in viral clearing. We conclude that early endoscopic evaluation for CMV is indicated in heart and heart-lung transplant patients with gastrointestinal symptoms. This study further suggests that intravenous ganciclovir therapy is effective for the treatment of gastrointestinal CMV in these patients.