OBJECTIVE We aimed to study the risk factors for first and subsequent cytomegalovirus (CMV) infection among patients who are CMV seropositive and underwent allogeneic hematopoietic cell transplantation (HCT). METHODS We performed an historical cohort study of all sequential CMV-seropositive patients who underwent allogeneic HCT at a single center. Between May 2007 and December 2012, 121 patients fulfilled inclusion criteria. RESULTS Multivariate model identified myeloablative preparative regimen (hazard ratio [HR] = 4.297, P = 0.033) and acute graft-versus-host disease (GVHD) prior to infection (HR = 5.091, P = 0.021) as risk factors for first CMV infection. The cumulative incidences of first CMV infection for patients with 0, 1, and 2 risk factors were 52%, 71%, and 91%, respectively. Multivariate analysis identified the diagnosis of lymphoma/myeloma (HR = 3.5, P = 0.049) and GVHD (HR = 1.280, P = 0.045) as risk factors for subsequent CMV infection. High graft CD3 stem cell dose was associated with a trend of lower rate of subsequent CMV infection (HR = 0.543, P = 0.056). The cumulative incidences for subsequent CMV infection in patients with 0, 1, and 2-3 risk factors were 11%, 41%, and 77%, respectively. CONCLUSIONS In conclusion, in CMV-seropositive patients, myeloablative conditioning and acute GVHD are risk factors for first CMV infection, while lymphoma/myeloma, ongoing GVHD, and low CD3 graft content are risk factors for subsequent infection.