18 of 49 pediatric renal transplant recipients, all of whom were on continual steroid and immunosuppressive treatment, were found to have warts. Although all 18 patients received treatment for this problem, only 5 had the warts successfully eradicated. The frequency of warts among transplant patients is three times that of the general childhood population and twice that of a group of nephrotic pediatric patients who received immunosuppressive therapy. We propose that drug-induced suppression of cell-mediated, and to a lesser extent, humoral immunity, may predispose people to develop warts.