Fifteen acutely ill patients (8 male, 7 female) aged 19 to 63 who met DSM-III criteria for schizophrenic disorder or schizophreniform disorder participated in a 4-week open trial of raclopride. The starting dose of raclopride was 2 mg increasing to 4 mg twice daily in the first week, further increments to 6 mg twice daily at day 14, and 8 mg twice daily at day 21 depending on response. Weekly assessments were made using the BPRS, Montgomery Schizophrenia Scale, Krawiecka-Goldberg Scale and Clinical Global Impression Scale. Extra-pyramidal symptoms and other side-effects were recorded weekly. Four patients failed to complete. Two were withdrawn because of clinical deterioration, and 2 others left hospital against advice after 2 weeks having shown initial improvement. Of the 11 completers, 4 were very much improved and 6 much improved; one was minimally worse. Extra-pyramidal symptoms were infrequent: 3 patients expressed occasional mild akathisia. Six patients complained of mild drowsiness. No major deviations were found in biochemical and physiological safety parameters. Plasma concentrations of raclopride were stable throughout treatment or proportional to dose changes. There was approximately a 6-fold inter-individual difference in steady-state drug concentrations. Plasma levels of prolactin increased transiently after raclopride intake to a maximum of up to 80 and 130 ng/ml in male and female patients respectively.