The authors studied basal HGH levels and HGH response to insulin-induced hypoglycemia in 12 schizophrenic patients who had been treated with 200--450 mg/day of chlorpromazine for 6 months to 4 years compared with 12 schizophrenic patients who had received no drugs and 15 normal control subjects. They found no significant differences among the three groups in basal HGH levels or in maximum response HGH levels. No significant correlation was found between duration or dose of chlorpromazine therapy and HGH secretion. Longitudinal study in 5 previously untreated schizophrenic patients during 13 weeks of chlorpromazine administration showed a nonsignificant reduction in HGH response. Thus, the authors' findings fail to demonstrate any significant effect of chlorpromazine on growth hormone secretion in man.