OBJECTIVE: This study aimed to assess the cost effectiveness of ziprasidone versus haloperidol in sequential intramuscular (IM)/oral treatment of patients with exacerbation of schizophrenia in Spain. METHODS: A cost-effectiveness analysis from the hospital perspective was performed. Length of stay, study medication and use of concomitant drugs were calculated using data from the ZIMO trial. The effectiveness of treatment was determined by the percentage of responders (reduction in baseline Brief Psychiatric Rating Scale [BPRS] negative symptoms subscale >or=30%). Economic assessment included estimation of mean (95% CI) total costs, cost per responder and the incremental cost-effectiveness ratio (ICER) per additional responder. The economic uncertainty level was controlled by resampling and calculation of cost-effectiveness acceptability curves. RESULTS: A total of 325 patients (ziprasidone n = 255, haloperidol n = 70) were included in this economic subanalysis. Ziprasidone showed a significantly higher responder rate compared with haloperidol (71% vs 56%, respectively; p = 0.023). Mean total costs were euro3582 (95% CI 3226, 3937) for ziprasidone and euro2953 (95% CI 2471, 3436) for haloperidol (p = 0.039), mainly due to a higher ziprasidone acquisition cost. However, costs per responder were lower with ziprasidone (euro5045 [95% CI 4211, 6020]) than with haloperidol (euro5302 [95% CI 3666, 7791], with a cost per additional responder (ICER) for ziprasidone of euro4095 (95% CI -130, 22 231). The acceptability curve showed an ICER cut-off value of euro13 891 at the 95% cost-effectiveness probability level for >or=30% reduction in BPRS negative symptoms. CONCLUSIONS: Compared with haloperidol, ziprasidone was significantly better at controlling psychotic negative symptoms in acute psychoses. The extra cost of ziprasidone was offset by a higher effectiveness rate, yielding a lower cost per responder. In light of the social benefit (less family burden and greater restoration of productivity), the incremental cost per additional responder with sequential IM/oral ziprasidone should be considered cost effective in patients with exacerbation of schizophrenia in Spain.