BACKGROUND: Compliance is an important factor for successful clinical management of schizophrenia. Risperidone long-acting injection (RLAI) can improve compliance compared to oral atypical anti-psychotics and several studies found the use of RLAI was associated with reduced hospitalization. RLAI was introduced to Japanese practice from June 2009 and is currently only available atypical anti-psychotic depot medication.  OBJECTIVES: To assess the impact of RLAI use on hospitalization as a proxy of relapse in daily practice among Japanese patients with schizophrenia. METHODS: Mirror image comparison of psychiatric related hospitalization was made for 6 months before (pre-RLAI) and 6 months after (post-RLAI) the initiation of RLAI.  The data source was commercially available health insurance claims database (Japan Medical Data Center, Tokyo; January, 2009 to June, 2011). The inclusion criteria were patients (20-59 years of age) who were diagnosed with schizophrenia (ICD F20 to F29) and who had continuous enrollment of the Group health insurance for 6 months before and 6 months after the initiation of RLAI. Patients with long-term hospitalization (>6 months) were excluded.  Additionally, study patients were restricted to have at least 3 month continuous treatment with RLAI. In the analysis the initiation of RLAI during hospitalization contributed to pre-RLAI hospitalization because previous treatment was considered as failure. RESULTS: A total of 25 patients from 58 patients who were initiated on RLAI met the inclusion criteria. Twenty patients started at outpatient visits and 21 patients continued the RLAI treatment after 6 months. Mean dose was 33.5mg. The proportion of patients requiring psychiatric hospitalization was changed from 28% to 8% between pre- and post-initiating RLAI (P<001). The total number of psychiatric hospitalization was reduced by 82% (11 vs. 2, P=0.02).   CONCLUSIONS: Switching from oral anti-psychotics to RLAI may impact on the reduction in hospitalization among Japanese schizophrenic patients. Further investigation is necessary.