Computer systems such as CAD, PDM, and SCM have been introduced to the manufacturing industry. However, these systems are heterogeneous. The product data exchange between heterogeneous CAD and PDM systems is a crucial issue for the integration of product development systems. STEP offers an efficient mechanism of product data exchange between heterogeneous systems. This thesis introduces a UML-based mapping methodology for the product data models. The suggested mapping method has been applied to the mapping of product structure data between CAD and PDM systems, and the STEP to XML mapping for the exchange of BOM and catalogs. Based on the STEP methods, we developed an interface module between a CAD system and a PDM system. Finally, the interface module has been applied to the industry examples.