• A study of the tuberoinfundibular dopamine tract was undertaken in chronic schizophrenic patients with and without tardive dyskinesia. Biochemical evidence of the purported dopamine receptor supersensitivity in tardive dyskinesia was sought by demonstrating a hyperresponse of growth hormone and prolactin to dopamine agonists. Contrary to this prediction, no endocrine supersensitivity occurred in the tardive dyskinesia patients. Rather, a significantly decreased response to dopaminergic stimualtion was demonstrated in the total chronic schizophrenic group.