We observed an epidemic of parainfluenza type 3 viral infection in a renal transplantation service among 16 recent transplant recipients. To assess the effect of infection on transplant function, we retrospectively compared the infected patients with a matched, uninfected control group. In addition to symptoms of a mild upper respiratory tract infection associated with the epidemic, there was an increase in the frequency of acute rejection episodes during the period of infection in the infected group. Nevertheless, outcome in terms of patient and graft survival at six months was not affected when compared with the survival rates of the control group.