The atypical antipsychotic zotepine was compared to haloperidol in 126 patients suffering from acute exacerbation of schizophrenia (DSM-III-R) in a randomized, double-blind study. After 8-weeks, 150 to 300 mg zotepine improved scores on the Brief Psychiatric Rating Scale (BPRS) more than 10 to 20 mg haloperidol (-17.03 versus -13.45; 95%CI for zotepine-haloperidol -9.34/2.04). BPRS subscores and Clinical Global impressions (CGI) Severity and improvement subscales showed comparable gains, but scores on the Scale for the Assessment of Negative Symptoms (SANS) improved significantly more with zotepine (-23.82) than haloperidol (-15.15; P < .05; 95%CI for zotepine haloperidol -18.03/-0.18). Adverse events were reported by 71 percent of zotepine and 78 percent of haloperidol patients. Extrapyramidal side effect (EPMS) scores decreased with zotepine (-0.34) but increased with haloperidol (+2.32; P < .05). Seven haloperidol patients reported akathisia but no zotepine patients did (p < .05). Uric acid reductions (which appear to have no clinical consequence) and transient raised liver enzymes were recorded with zotepine. Weight increased on zotepine (2.32 kg; P < .001) and a small increase in pulse rate occurred (P < .05). Both drugs were effective in reducing positive symptoms of schizophrenia; zotepine was significantly more effective against negative symptoms and reduced EPMS.