The objective of this study was to assess the pharmacoeconomic impact of olanzapine in the treatment of schizophrenic patients resistant to conventional antipsychotic drugs. The study was an open-label, multicentre, 'mirror-image', pilot study. Resource utilisation during the 6 months prior to starting olanzapine treatment was retrospectively collected for all patients (period A) at the beginning of the study. Use of direct medical resources was collected after 6 months of olanzapine treatment initiation (period B). The study was conducted in the psychiatric research units of general hospitals, and included 25 treatment-refractory schizophrenic patients. Olanzapine therapy was initiated at 15 mg/day on a single daily dose from day 1. The dosage could be adjusted at any time within the range of 10 to 25 mg/day, targeting the optimum balance between response and adverse effects. Patients were evaluated using the following efficacy rating scales: PANSS in its Spanish validated version, BPRS, CGI severity and improvement scales and Patient Global Impression of Improvement. Medical resource use was collected at the beginning of the study for the 6 months prior to treatment, and at the end of the study for the 6 months of olanzapine treatment. The response rate according to the previously defined response criteria was 36% (9 of 25) at 6 weeks and 48% (12 of 25) at 6 months. Despite the higher costs (given in pesetas; Pta) of medication in period B compared with period A, total direct medical costs were higher in period A (Pta884 098) compared with period B (Pta850 974), although the difference did not reach statistical significance. The difference in acute psychiatric hospitalisation days was the main contributor to the difference in total hospitalisation costs (31 +/- 37 in period A compared with 21 +/- 30 in period B) [p = NS]. The results suggest that olanzapine may be effective in a significant number of neuroleptic-resistant schizophrenic patients, and that the efficacy obtained does not necessarily imply an increase in the cost of the treatment.