Zotepine, a new neuroleptic, was administered to 23 hospitalized patients with schizophrenia at doses of 75 to 600 mg/d for 21 to 42 days. Based upon analysis of conventional rating scales we observed a significant improvement (P less than 0.001) during week 1, which compound throughout the study period. After 21 days we identified 17 responders and 6 nonresponders, 2 of whom dropped out of the study because of a tonic-clonic seizure in one case and withdrawal of consent to further participation in the second case. During further treatment the improvement remaind stable in the responder group, while 1 nonresponder improved after 3 weeks of treatment. In 9 patients extrapyramidal symptoms were observed (6 parkinsonism, 2 early dyskinesia, 1 parkinsonism and early dyskinesia), which required sporadic (n = 3) or continuous (n = 2) treatment with biperiden in 5 cases. This low incidence of extrapyramidal symptoms necessitating coadministration of anticholinergic drugs suggests that the risk of inducing parkinsonism and dyskinesias during zotepine treatment is low. Comparison of cortisol, growth hormone and prolactin release in normal controls challenged with 25 mg zotepine showed that only prolactin secretion is increased, while secretion of cortisol and growth hormone remains unaffected. The clinical effects observed in the present study show that zotepine has potential value in the treatment of schizophrenia. The findings warrant further study in controlled trials.