This is a preliminary study of the treatment of 36 patients with Peyronie's disease who received tamoxifen 20 mg twice daily for 3 months. An improvement occurred in 16 of 20 patients with penile pain, in 11 of 31 patients with an erectile deformity and 12 of 35 patients had a plaque shrinkage of at least 1 cm. Some improvement occurred in 6 of the 8 patients with a histologically confirmed inflammatory infiltrate of the plaque but not in any of the 4 patients without an infiltrate. The inflammatory infiltrate was found in patients in whom the duration of the disease was less than 4 months.