Nafarelin 400 micrograms daily and danazol 600 mg daily were compared in a double-blind randomized study. Eighty-two patients with endometriosis were treated for 6 months after an initial laparoscopy and 74 had a second laparoscopy. Twenty-two (30%) patients had complete disease regression, 42 (57%) patients had a partial regression, and in 10 (13%) patients disease was unchanged or worse. Both treatments led to significant regression of active disease but not of adhesions. At 3 months follow-up, 34 (64%) patients reported their symptoms were improved, 15 (28%) reported no change, and 4 (8%) were worse. Nafarelin was associated with more hot flushes and headaches, and danazol with more weight gain. No significant differences, however, were noted in treatment efficacy between the two groups.