Synthetic luteinizing hormone-releasing hormone (LHRH) was administered intravenously in a dose of 25 mug to 9 patients with Turner's syndrome of 45,XO karyotypes, 5 normal menstruating women, and 5 postmenopausal women. In patients with Turner's syndrome, the basal serum LH level was higher than that of the normal subjects and lower than that of postmenopausal women. The LH response to LHRH, when expressed as a percent of control, was comparable to that of the normal luteal phase and significantly higher than that of postmenopausal women. The basal FSH level was more elevated than the basal LH level. The FSH response to LHRH, when expressed as a percent of control, was similar to that of postmenopausal women and lower than that of normal subjects. The results suggest that pituitary function is preserved in patients with Turner's syndrome. I interpret the pituitary responsiveness and/or reserve of patients with Turner's syndrome as larger than that of postmenopausal women. A greater response of LH than of FSH to LHRH was observed in this study and is contrary to findings reported by others on teenage patients with Turner's syndrome. This suggests that the sensitivity of gonadotropins changes with age in Turner's syndrome.