Obese patients who voluntarily reduce to a normal weight may develop secondary amenorrhea. Six young women who dieted to lose from 13 to 50 pounds, including four from an obese weight, were evaluated because of absent cervical mucus ferning, hypoestrogenic vaginal smears, and failure to have withdrawal menses from a progestogen. Serum FSH values were normal in all, while four had normal serum LH and two had low serum LH levels. T4 and/or T3 uptake was normal in all. The pituitary-adrenal axis was apparently intact since baseline urinary steroids were normal as was the response to both ACTH and metyrapone. Fasting serum growth hormone was markedly elevated in two and slightly elevated in three, with the other patinet demonstrating an unusually high response to glucagon/propranolol in the 30 minute specimen. These endocrine findings are similar to those observed in patients with anorexia nervosa, but the weight loss is entirely voluntary and there was no associated psychiatric abnormality.