A double-blind trial was carried out comparing the effects of decanoates of flupenthixol and fluphenazine on the symptoms, ward behaviour and functional capacity in occupational therapy in 51 chronic schizophrenic patients. The patients were carefully selected on the basis of rigid criteria for diagnoses. To exclude nonresponders to neuroleptics the patients were first taken off neuroleptic drugs and only those who appeared to show deterioration were included in the trial. The dosage of drugs was varied according to clinical indications. The length of the trial was initially 4 months and 31 patients were followed for an additional 4 months. To ensure reliability multiple assessments were made at the start and the end of the trial. Most of the statistical tests showed no differences between the treatments, but some of those relating to affective symptoms showed an advantage for flupenthixol as compared with fluphenazine. There were no differences in the incidence of extra-pyramidal side-effects which required treatment in only 32% of the patients on each drug.