OBJECTIVE: This multicenter, double-blind, placebo-controlled study evaluated the efficacy and safety of three doses of sertindole (12, 20, and 24 mg/day) and haloperidol (4, 8, and 16 mg/day) in the treatment of psychotic symptoms for 497 hospitalized patients with schizophrenia. METHOD: The patients were randomly assigned to one of the medication groups and received treatment for 8 weeks. Changes in Positive and Negative Syndrome Scale, Scale for the Assessment of Negative Symptoms, Brief Psychiatric Rating Scale, and Clinical Global Impression scores were used as evaluations of treatment efficacy. Three rating scales were used to assess extrapyramidal symptoms as well as the occurrence of adverse events and the use of medications related to extrapyramidal symptoms. RESULTS: Both sertindole and haloperidol were comparably effective in the treatment of psychosis, and all dose levels were significantly more effective than placebo. For the treatment of negative symptoms, only sertindole, 20 mg/day, was significantly more effective than placebo. For all extrapyramidal symptom measures, sertindole was clinically and statistically indistinguishable from placebo, and rates of extrapyramidal symptoms were not dose related. All dose levels of haloperidol produced significantly more extrapyramidal symptoms than placebo or sertindole. Adverse events associated with sertindole treatment were mild in severity. CONCLUSIONS: Sertindole is a new antipsychotic agent effective for the treatment of both the positive and negative symptoms of schizophrenia, with motor side effects that are indistinguishable from those associated with placebo.