CMV pneumonia is rare following ABMT. No information has been presented concerning risk factors or outcome of antiviral therapy. Information concerning CMV pneumonia after ABMT was collected from bone marrow transplant centers in Europe. Twenty-one patients who fulfilled the diagnostic criteria of CMV pneumonia were reported. Eighteen of these patients were reported from centers who also reported the total number of ABMT performed. The CMV pneumonia frequency among 2252 reported ABMT patients was 0.8%, and this varied from 0% to 8.6% between different centers. Survival for > 30 days from diagnosis of pneumonia was 43%. Three patients suffered relapses, which were fatal, giving a total survival of 28%. Patients treated with or without TBI had a survival of 18% and 50%, respectively. Among patients given ganciclovir or foscarnet with or without intravenous immune globulin, survival at 30 days was 50% and total survival 28%. There was no difference in survival with or without the addition of intravenous immune globulin. CMV pneumonia is an infrequent but serious complication of ABMT.