The purpose of this trial was to assess the potential utility of adjunctive treatment with a typical neuroleptic for patients with refractory psychosis insufficiently responsive to clozapine alone. Seven chronic schizophrenic or schizoaffective patients who remained stabilized for at least 9 months on clozapine received open clinical trials with adjunctive loxapine lasting from 18 to 50 weeks. Their symptoms were documented with periodic Brief Psychiatric Rating Scale assessments. All patients improved at least somewhat and two improved remarkably. In the four cases in which the assessment was made, the loxapine had no apparent effect on plasma clozapine levels. We conclude that adjunctive treatment with typical neuroleptics for patients with an incomplete response to clozapine merits further investigation.