An increased incidence of late cytomegalovirus (CMV) infection has been reported during the last decade since the introduction of ganciclovir (GCV) prophylaxis or GCV pre-emptive therapy. Given that a donor lymphocyte infusion (DLI) can induce more severe GVHD, this may predispose a patient to late CMV infection. In all, 64 patients (median age 36, M/F 38/26) underwent allogeneic stem cell transplantation (SCT) using a matched sibling donor with bone marrow (n=9) or peripheral blood stem cells (n=55). The overall incidence of CMV infection, early and late CMV infection was 46.9 (30/64), 42.2 (27/64), and 16.4% (9/55), respectively. Early CMV infection was treated with GCV pre-emptive therapy that produced a 92.6% success rate. Among the 20 patients who received 35 DLIs, late CMV infection developed in eight (42.1%) of 19 evaluable cases with a median onset at 127 days post transplant. Risk factors for late CMV infection in a logistic regression analysis included DLIs (P=0.001) and a previous history of CMV infection (P=0.006). In conclusion, late CMV infection was strongly associated with DLIs and a previous history of early CMV infection. Accordingly, extended surveillance of CMV antigenemia is recommended for patients receiving DLIs or who have a previous history of CMV infection.