LH, FSH, PRL and testosterone were estimated by radioimmunoassay in serial venous samples from 20 male chronic schizophrenic patients, 17 age-matched controls, 3 patients in remission from acute schizophrenia, and in single samples from age-sex matched populations. LH and FSH, but not testosterone or PRL, were significantly reduced in patients with chronic schizophrenia. There was an associated reduction in the frequency, but not amplitude, of LH secretory episodes in patients with chronic schizophrenia. No abnormalities of LH secretion were detected in those patients in remission from acute schizophrenia. Fourteen of the chronic schizophrenic patients were retested at a later date with similar results, except in the case of the few patients who had been started on neuroleptic medication. Some relationships were established between hormonal secretion and the clinical features of these patients. The possible significance of these findings is discussed in the context of the complex control of gonadotropin secretion from the anterior pituitary and the natural history and nature of chronic schizophrenia.