Antigenadetropin (Danazol) was administered to 39 patients with endometriosis diagnosed at laparoscopy and confirmed by laparoscopic biopsy. None of the patients had surgical resection of the lesion prior to the treatment. While on the drug, all patients developed evidence of ovarian suppression both in regard to ovulation and steroidogenesis. The results were evaluated by repeat laparoscopy and biopsy. The extent of the disease was documented before and after treatment by photography and drawing. There was marked decrease in the extent of endometriosis after treatment: 59% of patients had no evidence of disease, 26% had peritoneal adhesions and hemosiderin deposits but no active endometriosis, and 15% had residual endometriosis. Histology in the latter group revealed atrophic changes in the uterine and ectopic endometrium and the evidence of a healing process.