Replacement of antipsychotic drugs with quetiapine (QTP) was tried in a naturalistic setting in chronic schizophrenic patients who still showed moderate psychiatric symptoms and either showed extrapyramidal symptoms (EPS) or took anti-parkinson drugs for the EPS. QTP was added on and gradually increased while the previous drugs were tapered and discontinued whenever possible. Clinical symptoms, objective and subjective QOL, and EPS were measured before and 6 months after QTP addition, using Brief Psychiatric Rating Scale (BPRS), Quality of Life Scale (QLS), Schizophrenia Quality of Life Scale (SQLS) and Drug-Induced Extrapyramidal Symptom Scale (DIEPSS), respectively. Twenty-one patients completed the trial and received the assessment. It was found that replacement with QTP-improved clinical symptoms, objective and subjective QOL and EPS. This improvement was equally observed in not only patients who switched to QTP monotherapy (n = 11) but also patients who took QTP together with reduced small doses (4.4 +/- 4.3 mg/day) of previous drugs (n = 11). The results suggest that replacement with QTP improves symptoms as well as objective and subjective QOL in a subgroup of schizophrenia.