Cytomegalovirus (CMV) infection was detected in 65 of 143 (45%) autologous bone marrow transplant (BMT) patients. CMV pneumonitis occurred in only 2% of the patients and CMV retinitis occurred in none. Infection occurred in half of the 40 initially seronegative patients and 47% of the 94 initially seropositive patients. Among initially seropositive patients, platelet recovery was slower in infected patients than in those not infected (97 v 35 days median, P = .003), and neutrophil recovery was slightly delayed in infected patients (31 days v 24 days, P = .02). Although the incidence of CMV infection was comparable in autologous and allogeneic BMT patients, CMV pneumonitis was less frequent in autologous BMT patients (2% v 12%, P less than .001). The risk for CMV pneumonitis in autologous BMT patients was comparable with that in allogeneic BMT patients without graft-v-host disease (GVHD) (2% v 6%), but significantly lower than the risk in allogeneic BMT patients with GVHD (2% v 23%, P less than .001).