Objective: efficacy and safety of change from haloperidol to olanzapine was evaluated in a sample of homogeneous population of Peruvian schizophrenic patients with extrapyramidal symptoms. Methods: thirty Peruvian patients with schizophrenia (DSM-IV criteria) were changed from haloperidol ≤20 mg/d to olanzapine 10 to 20 mg/d for eight weeks. Potential changes in the extrapyramidal symptoms observed in all the patients at study baseline were evaluated using Simpson Angus Scale (SAS) and Barnes Akathisia Scale (BAS). Brief Psychiatric Rating Scale (BPRS), positive and negative Syndrome Scale (PANSS) and Clinical Global Im-pression Severity (CGI-S) were also administered to evaluate changes in efficacy. Additionally, Quality of Life Scale (QLS) was used and adverse events were registered. Results: multivariate analysis found a statistical decrease in SAS, BPRS, PANSS and QLS (p< 0.001) and BAS (p< 0.006) change was registered from the first week of olanzapine administration in all scales. Forty percent of patients experienced some type of adverse events during the trial, with constipation and weight gain being reported most frequently. Conclusions: switching from haloperidol to olanzapine could offer not only a reduction in extrapyramidal symptoms, but also an improvement in efficacy measures and quality of life in the treatment of this sample of Peruvians patients with schizophrenia. ©INNN, 2006.