Epidemiologic and clinical characteristics of cytomegalovirus (CMV) infection and disease were analyzed retrospectively in 159 autologous marrow transplant recipients. The probability of CMV infection by day 100 after transplant was 22.5% in patients seronegative to CMV before transplant versus 61.1% in seropositive patients (P less than .0001 by logrank test). Multivariate analysis identified positive pretransplant CMV serology as the only definable risk factor for CMV infection (relative risk 1.4, P less than .0001). CMV pneumonia developed in 11 patients at a median time of 100 days after transplant and was fatal in nine cases. CMV pneumonia was associated with significantly decreased probability of survival by day 100 after transplant (relative risk of death of 16.7, P less than .0001). In contrast to earlier reports, CMV infection had no significant effect on the rapidity of platelet or neutrophil recovery after transplant as assessed by time-dependent multivariate analysis. Because the incidence of severe CMV disease is not negligible after autologous marrow transplantation, preventive measures against CMV infection are warranted, as in allogeneic marrow transplantation.