The prevalence, incidence, and source of infections with different types of herpes-viruses were determined prospectively for 25 persons undergoing hemodialysis, 30 allograft recipients, and 16 kidney donors. The prevalence of prior infections with cytomegalovirus (CMV), herpes simplex virus (HSV), and Epstein-Barr virus (EBV) was high (72%–100%) and was similar for healthy persons and those with renal failure. The incidence of infections in patients undergoing hemodialysis was no greater than that before dialysis. In allograft recipients, the incidence of infection with CMV was 73%; HSV, 57%; EBV, 30%; and varicella-zoster virus (clinical), 7%. Ninety-seven percent of the patients developed an infection with one or more herpes-viruses. Transfusions, hemodialysis, the allograft, and hospital environment were not significant sources in transmission. Uremia and splenectomy were unimportant in the reactivation of infection. Immunosuppressive drugs possibly augmented by a graft rejection response account for the high incidence of recrudescent infections with CMV and HSV.