A total of 56 cases with warts in which podophyllin treatment was either contraindicated or a failure, were treated with nitrous oxide using a Keymed 500 cryosurgical appliance. Forty-three patients who completed treatment were followed-up for three months. Thirty-seven of these had received applications of podophyllin twice weekly for an average period of three months before cryosurgery. The remaining cases in whom podophyllin was considered to be contraindicated included five with vulval warts (two were pregnant, two were bronchial asthmatics taking oral prednisolone, and one was taking oral clomiphene citrate), and a diabetic patients with penile warts. Thirty-two were cured and 11 relapsed. The latter were re-treated at the end of the follow-up period with two freezing cycles of 45 seconds at an interval of 30 minutes. Seven were cured and the remaining four men who failed to respond belonged to the podophyllin-resistant group and included three with metal warts and one homosexual with anogenital warts. Cryosurgery gave a cumulative success rate of 91%. A single freezing cycle was free from complications but a double freezing cycle was often followed by severe local reaction.