Human cytomegalovirus (HCMV) infection is the single most frequent infectious complication in the early period after kidney transplantation. The HCMV load in blood, measured by HCMV PCR or the HCMV pp65 antigen test, is a predictor of HCMV disease in seropositive recipients. However, plasma virus load measurements are of only modest value in predicting the risk of HCMV disease in seronegative recipients of kidneys from seropositive donors. HCMV infection is an independent risk-factor for acute kidney graft rejection. There is also evidence that HCMV is associated with an increased long-term mortality and post-transplant diabetes mellitus. Whether pre-emptive or prophylactic therapy should be the preferred strategy is not yet decided. Some studies indicate that HCMV prophylaxis may reduce the risk of acute rejection, and thereby increase long-term graft survival in seronegative recipients of kidneys from seropositive donors.