Abstract Background and Aims Cytomegalovirus (CMV) infection is an important complication in immunocompomised patients. Although approach to CMV infection is well-defined in stem cell and solid organ transplant recipients, less is known about the frequency and risk factors of CMV disease in patients with glomerulonephritis (GN). As few studies have shown that cyclophosphamide (CYC) treatment is a risk factor for CMV infection in GN patients, we aimed to describe the frequency and risk factors of CMV infection in GN patients treated with CYC. Method 268 patients diagnosed GN between January 2017 and November 2019 in Ankara University İbni Sina Hospital, Nephrology Department. We recruited 43 GN patients who were treated with CYC and screened all patients for viral DNA monthly. CMV infection defined by CMV DNA detected >500 copies/µl. Patients developed CMV and no-CMV infection were compared for age, sex, glomerular pathology, renal function and clinical status before and after treatment. Results CMV infection was detected in 10 (23,3%) patients at 2±1 (min:1 max:3) months of CYC treatment (Table-1). 7 patients were treated for CMV infection with parenteral ganciclovir, while the other 3 patients with low CMV DNA level (509, 538 and 540 copies/ml) and no disease symptoms were monitored without antiviral treatment. Patients with CMV infection had higher serum creatinine (4,2±3,2 vs. 1,9±1,8 mg/dl, p=0,006), lower estimated glomerular filtration rate (29±11 vs. 65±8 (ml/min/1.73 m2, p=0.016), lower low-density lipoprotein (144±71 vs. 221±83 mg/dl, p=0,012) at diagnosis compared with no-CMV infection patients (Table-2). Also more patients were diagnosed with rapidly proggressive GN (80,0% vs. 27.3%, p=0,007), and secondary GN was the most common GN diagnosis (80,0% vs. 27.3%, p=0.007) in CMV infection group. Conclusion CMV infection is a common complication in GN patients treated with CYC. Routine monitoring and prophylaxis should be considered for the patients who have risk factors for CMV infection.