The purpose of this study was to assess the tolerability and efficacy of 150-600 mg remoxipride (predominantly a DA2 receptor antagonist) in an open long-term (1 year) multicentre trial in chronic schizophrenic patients. The mean duration of illness before entering the study was 21 years and the pre-study neuroleptic dosage in chlorpromazine equivalents was 930 mg/day. The clinical efficacy was measured with the Brief Psychiatric Rating Scale and the Clinical Global Impression scale. The adverse events were recorded by a 26-item Adverse Symptom Checklist and by the Abnormal Involuntary Movements Scale. Forty-five patients were included in the study. The mean daily dose of remoxipride during the last week of treatment was 378 mg. Eighty percent (36 patients) withdrew prematurely (< 1 year). The main reasons for withdrawal were: ineffectiveness (n = 15), treatment refusal (n = 12) and adverse events (n = 8). The most frequently reported adverse events were insomnia (n = 20) and tiredness (n = 7), whereas only a few (n = 6) extrapyramidal symptoms were reported. There was no relationship between remoxipride plasma concentration and clinical efficacy nor was any relationship found between the ratio of pretrial chlorpromazine equivalent to last remoxipride dose and the therapeutic effect. Remoxipride alone seemed to have an insufficient neuroleptic efficacy in these chronic and treatment-resistant schizophrenic patients but was well tolerated.