Purified clostridial collagenase was determined intralesionally in 31 men with Peyronie's disease. Within 4 weeks of treatment 20 patients showed an objective improvement. Pain was eliminated in 13 of 14 patients with this complaint at presentation within the same 4-week period. The ability to have intercourse was restored in 3 of 4 patients with this problem. Except for a small corporeal rupture of the site of injection in 1 patient, no significant untoward effects were noted. During the mean 9.8-month followup 1 recurrence of bending was noted.