This study evaluated the overall effectiveness and tolerability of atypical antipsychotics (risperidone vs. olanzapine vs. quetiapine) used in the treatment of bipolar inpatients. After screening 463 patients, the medical records of 158 inpatients with bipolar I disorder, who were given olanzapine, risperidone or quetiapine as adjuncts to mood stabilizers for at least 1 month and not administered with any other antipsychotics, were examined. Details of the tolerability and effectiveness were reviewed according to the treatment records during their hospital stay. The results showed equivalent effectiveness based on the Clinical Global Impression (CGI) and Global Assessment Functioning (GAF) score between the three atypical antipsychotics. The frequency of the extrapyramidal symptom-related side effects were higher in the risperidone-treated group than in the olanzapine and quetiapine-treated group. This suggests that risperidone, olanzapine and quetiapine have a comparable effectiveness in inpatients with bipolar I disorder in a naturalistic setting. However, there were some differences in tolerability between these results as reported from previous Western studies.