In contrast to allogeneic bone marrow transplantation (allo-BMT), there is a paucity of data on cytomegalovirus (CMV) infection and preemptive therapy (PT) strategies following allogeneic peripheral blood stem cell (allo-PBSC) transplantation. We report here on the patterns of CMV infection in a cohort of 225 patients following sibling donor allo-PBSC transplantation. In an attempt to reduce neutropenia, we used intravenous low-dose short-course (LDSC) ganciclovir (GCV) 5 mg/kg once daily for 21 days as preemptive therapy. A total of 165 recipient-donor pairs were CMV seropositive. An initial episode of viremia (detected by shell vial/tube culture) occurred in 75/165 (45%) at a median of day +35 (17-445) post allo-PBSC. In all, 58 patients received PT with LDSC GCV. Among 58, 55 (94%) completed the 21-day course of PT. A second episode of viremia occurred in 19/58 (33%) at day+80 (50-174) and a third episode in 5/58 (9%) at day+134 (103-218). Among patients receiving LDSC GCV, 5/58(9%) developed disease (four pneumonia, one colitis) at day+211 (63-487). No patient on LDSC GCV exhibited a decline in their ANC below 500/microl and none required growth factors. LDSC GCV is extremely well tolerated and cost-effective as PT for CMV viremia following allo-PBSC transplantation.