The Diagnosis Procedure Combination (DPC) is a case-mix classification system that is linked with a lump-sum payment system for inpatient care reimbursement. The key objectives of introducing the DPC system are to implement an electronic claim system and to provide transparency of hospital performance. The DPC data include discharge abstract and administrative claims data. The unique advantage of the DPC data is the inclusion of detailed process data and several clinical data that can be applied to clinical studies. In this report, we explain the structure and contents of the DPC database, and discuss the applicability of the DPC data to clinical studies, comparing them with the US Nationwide Inpatient Sample database.