Plasma estradiol (E<sub>2</sub>), serum LH and FSH, and the gonadotropin response to two consecutive LHRH administrations (10 and 100 µg with an interval of 2 h) were determined in 19 patients with anorexia nervosa (AN) at the emaciation phase, before and after estradiol benzoate (E<sub>2</sub>B) injections (3 µg/kg/day for 7 days). The same investigations were repeated after weight restoration in 9 AN atients who remained amenorrheic. Both at the emaciation phase and after weight restoration, E<sub>2</sub>B enhanced the second LH response to LHRH and decreased serum FSH, suggesting that the functional capacities of the pituitary gonadotrophs are normal in AN. Unlike E<sub>2</sub>B injections, weight restoration increased all the hormone values, suggesting that the weight restoration effects on the abnormal gonadotropin secretory pattern of AN depend on another mechanism than the E<sub>2</sub> lowering. That mechanism is probably a disorder of the hypothalamic LHRH secretion, the consequences of which could be reinforced by the low E<sub>2</sub> levels.