SUMMARYBasal serum concentrations of LH and FSH and their response to LHRH were studied in twelve pre‐ and ten post‐menopausal women with Cushing's syndrome before and after treatment. Subnormal basal concentrations of LH were found in twelve out of twenty‐two, and of FSH in ten of the twenty untreated patients. There was a correlation between the urinary free cortisol (UFC) and basal LH values, r =−0·59 (P<0·05), and UFC and basal FSH values, r=−0·76 (P1080 nmol/24 h (normal range<270) had both a subnormal basal gonadotrophin level and a subnormal response of at least one gonadotrophin to the releasing hormone. In those patients in whom successful remission was obtained and who did not require replacement therapy, subnormal basal gonadotrophins were usually restored towards or into the normal range. It is concluded that while gonadotrophin levels may be normal in women with Cushing's syndrome, they are subnormal in those with the highest cortisol values. This may be due to a direct suppressive effect of cortisol on the release of stored pituitary hormone, and/or on LHRH release from the