In clinical setting, treatment-refractoriness, medication induced tardive dyskinesia and amenorrhea in chronic schizophrenia are frequently problematic. However, there are few guideline solving these problem available to clinicians. The goal of this study was collecting clinical data on clinical effectiveness and predictors of response of switching to olanzapine. We attempted to switch to olanzapine from risperidone and clozapine in chronic 31(risperidone 17, clozapine 14) schizophrenia and schizoaffective disorder patients suffering from sustained symptoms, weekly blood monitoring, medication induced tardive dyskinesia and amenorrhea. Previous antipsychotics dosage was gradually decreased for 2 or 3weeks, at the same time olanzapine dosage was gradually increased. At baseline, after 1 week, after 2 weeks and after 4 weeks we checked Brief Psychiatric Rating Scale, Clinical Global Impression Scale, Sympson-Angus Rating Scale, Barnes Akathisia Rating Scale and followed up after 12 months. Successful switch after 4 weeks was achieved in 25 patients(clozapine 9(64.2%), risperidone 16(94.1%)). Overall, mean BPRS and CGI scores increased significantly. Successful maintenance after 12 months was achieved in 17 patients(clozapine 5(35.7%), risperidone 12(70.5%)). Overall, mean BPRS and CGI scores increased significantly too. Switching to olanzapine from other atypical antipsychotics is recommendable in chronic schizophrenia with treatment refractoriness and drug induced side effect.