Leukocyte depletion (LD) by blood product filtration has been shown to be similarly effective to the use of screened, CMV seronegative blood products to prevent CMV disease in CMV seronegative allogeneic stem cell transplant (SCT) patients with CMV seronegative donors. The aim of this retrospective study was to determine the risk for development of CMV infection requiring preemptive therapy and for CMV disease if unscreened products treated by prestorage LD is used. Forty-nine consecutive patients transplanted after June 1995 were included. As a control group, 33 patients transplanted from January 1992 to June 1995 in whom a combination of CMV seronegative and LD blood products were given. All patients were monitored weekly by a leukocyte-based PCR for CMV DNA detection. Preemptive therapy was initiated after two consecutively positive tests. No patient developed CMV disease in either group. CMV DNA was detected in 6/49 (p = NS) in the study group and in 3/33 patients in the historical control group. Two patients in the study group were given preemptive therapy compared to one patient in the control group. This study suggests that the risk for CMV disease and the need for preemptive therapy against CMV is low in CMV seronegative allogeneic SCT patients receiving grafts from CMV seronegative stem cell donors receiving LD blood products. Thus, this strategy can be safely used together with PCR monitoring and preemptive therapy.