To investigate the effects of medical treatment of endometriosis on concentrations of insulin and glucagon in comparison with those of androgens, 12 nonobese women with minimal endometriosis were randomly allocated to receive treatment with either danazol or the gonadotropin-releasing hormone analogue, goserelin. In subjects treated with danazol, mean (sd) summed serum insulin (1.08 (0.22) nmol/l pretreatment; 3.00 (1.50) nmol/l after treatment, p<0.05) and summed plasma glucagon (94 (21) pmol/l pretreatment; 238 (113) pmol/l after treatment, p<0.05) responses to oral glucose administration increased significantly, but remained unchanged in subjects treated with goserelin. In the danazol-treated group, the mean free testosterone index increased from 3.3 (1.6) to 13.3 (4.2) (p<0.01), but there was no correlation between either glucagon or insulin and free testosterone index. In the goserelin-treated subjects, however, there was no change in mean free testosterone indices (pretreatment 3.6 (1.0), post-treatment 3.9 (1.8). Thus, the increase in free testosterone index induced by danazol treatment is not responsible for the concomitant development of hyperinsulinaemia and hyperglucagonaemia.