The prolactin, cortisol and growth hormone (GH) responses to intravenous administration of 25 mg clomipramine (CMI) were studied in young male psychotic patients who had never received neuroleptics and suffered from schizophrenia (13 patients), delusional disorder (three patients) or schizoaffective disorder (one patient). The test was repeated after 1 month in 16 patients who were hospitalized and treated with haloperidol in doses appropriate for best clinical response (range: 7.5–40 mg daily). Symptomatology was assessed by the Brief Psychiatric Rating Scale (BPRS). There was no association of the side effects caused by the administration of CMI (nausea and emesis) to the GH responses. The side effects appeared significantly less in the after treatment trials. Treatment with haloperidol did not influence the response patterns of the three hormones. An indication that high haloperidol doses may inhibit the prolactin response to CMI was obtained when the data were compared between low (7.5–10 mg/day, mean 9.7) and high (15–40 mg/day, mean 22.0) dose subgroups. Significant positive correlations were found between the prolactin and cortisol responses to CMI in the drug-free state, and the scores in the positive symptoms subscale of the BPRS. The degree of improvement did not correlate to any of the hormonal data.