From 1966 to 1988, 98 of 108 patients with symptomatic Peyronie's disease received radiotherapy at our institution. In 11 of 61 patients (18%) who attended the clinic regularly for follow-up for longer than a year, new lesions distinct from the original lesions developed. This confirms that there is progression of the disease in a substantial number of cases after treatment. Long-term follow-up over an average of 111.5 months was achieved by means of a questionnaire in 47 of the 98 cases (48%). Forty-one of these patients (87.2%) had sexual intercourse after radiation. Twenty-eight of the 41 (68.3%) still have intercourse. Their average age at present is 59.6 years while the average age of the 13 patients (31.7%) not having intercourse is 70.9 years. The decline in sexual activity is thus age-related. Twenty-one of 25 patients (84%) experienced relief from pain, and angulation of the penis improved in 17 of 44 patients (38.6%) after radiotherapy. Radiotherapy may therefore be of benefit to patients with active Peyronie's disease and should be investigated in a randomised controlled study.