Cytomegalovirus (CMV) is an important pathogen after allogeneic transplantation. However, few studies have examined CMV reactivation after autologous peripheral blood stem cell transplantation (APBSCT) to treat multiple myeloma (MM), especially in the setting of the newer chemotherapeutic agents and/or 2 sequential APBSCTs (ie, tandem transplantation). A retrospective chart review of patients with MM who underwent either single APBSCTor tandem transplantation was conducted to evaluate the incidence, risk factors, and outcomes of CMV infection at a single institution. A total of 104 patients with MM underwent transplantation during the study period, including 66 patients who received tandem transplantation. The majority of patients (66 of 104; 63.5%) were CMV-seropositive, and CMV viremia was frequently detected in this subgroup (32 of 66; 48.5%). No primary CMV infections were identified. CMV reactivation was more common in recipients of tandem transplantation than in recipients of single APBSCT (P \.001). In addition, patients who developed CMV viremia were more likely to have received conditioning therapy with melphalan, bortezomib, dexamethasone, and thalidomide compared with those without CMV reactivation (P 5 .015). However, on multiple logistic regression analysis, only receipt of tandem transplantation was significantly associated with CMV reactivation (odds ratio, 5.112; 95% confidence interval, 1.27-20.60; P 5 .022). Febrile episodes of CMV viremia were observed in 17 patients (17 of 32; 53.1%), and invasive CMV disease was diagnosed in 1 patient. Our data suggest that CMV reactivation after APBSCT for MM is relatively common, and that viremia is often associated with fever. CMV surveillance should be considered, especially when tandem transplantation is performed using combination chemotherapy with high-dose melphalan.