It is difficult to access and share design data among heterogeneous CAD systems. Usually different CAD systems exchange design data using a neutral format such as IGES or STEP. A prototype STEP database has been implemented. The prototype system uses the OpenCascade geometric kernel and the commercial object-oriented database ObjectStore. STEP provides the database schema. The STEP database has been accessed and manipulated from commercial CAD systems of SolidWorks and Unigraphics. The data access module of the commercial CAD system has been developed by using the CAD system's native API, ObjectStore API, and ActiveX.