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 paper introduces a UML-based mapping methodology fur the product data models. The suggested mapping method has been applied to exchange the product structure data between a CAD system and a PDM system. Based on the STEP methods, we developed an interface module. (C) 2001 Elsevier Science Ltd. All rights reserved.