We analyzed the effect of cytomegalovirus (CMV) serostatus on overall survival (OS) and transplant-related mortality (TRM) in 253 consecutively treated patients receiving partially T cell-depleted (TCD) bone marrow from either matched related donors (MRDs; n=205) or matched unrelated donors (MUDs; n=48). Short-course, low-dose preemptive therapy with ganciclovir was provided as soon as a positive antigenemia assay result was obtained. Ganciclovir prophylaxis, which was identical to preemptive therapy, was given to patients with acute graft-versus-host disease (GVHD) grades II-IV who had to be treated with high-dose steroids. In recipients of transplants from MRDs, inferior OS and increased TRM were predicted by extensive chronic GVHD (P<.001). High-risk disease status and older age adversely influenced OS (P=.001) and TRM (P=.002), respectively; older age resulted in a trend toward decreased OS (P=.066). In recipients of transplants from MUDs, OS and TRM were strongly influenced by patient CMV seropositivity (P=.013 and.007, respectively). In conclusion, CMV seropositivity is not an adverse risk factor for OS and TRM in recipients of transplants from MRDs. However, in recipients of transplants from MUDs, patient CMV seropositivity strongly affects OS and TRM.