BACKGROUND: Cytomegalovirus(CMV) disease is an important opportunistic infection and contributes to significant morbidity and mortality in immunocompromised hosts. To determine predisposing conditions to CMV disease and its prognosis, the authors reviewed the clinical courses of patients with CMV disease. METHODS: We reviewed medical records of 23 patients with CMV disease diagnosed at Seoul National University Hospital from 1987 to 1997. RESULTS: CMV pneumonia was diagnosed in 8 patients. Underlying conditions of the patients were allogeneic bone marrow transplant(BMT) in 4 patients, lupus nephritis in 1, dermatomyositis in 1, and renal transplantation recipient in 1. The cumulative dose of corticosteroid given to the BMT recipients before the development of CMV pneumonia ranged between 1,000 and 4,700 mg, whereas that to the non-BMT patients ranged between 2,100 and 6,000 mg. Of the 8 patients with CMV pneumonia, five patients(75%) died. Of the 15 CMV gastroenteritis, two had CMV gastric ulcers. The gastric ulcers showed clinical and endoscopic improvement with systemic ganciclovir therapy. Among 13 patients with CMV enterocolitis, nine had preceding GI diseases, and nine had received systemic corticosteroids. Five patients died. The mortality was lower in patients with underlying bowel diseases than in those without ones(22% vs. 75%, respectively). CONCLUSION: The mortality of CMV disease was 62.5%, 0%, and 38% in patients with CMV pneumonia, gastric ulcer, and enterocolitis, respectively. GVHD, systemic corticosteroid and/or immunosuppressive therapy were major risk factors of CMV diseases.