Cellular changes of herpesvirus infection were found in 12 urine specimens from 4 renal allograft recipients. The cytologic diagnosis of herpes infection in the urine of renal allograft recipients has not been reported previously and is significant because of recent suggestions that viral infection contribute to allograft rejections. We were unable to find a consistent correlation between the cytologic diagnosis of herpesvirus and transplant rejection in the patients we studied.