Compared to PBL research on student learning outcomes, the issues surrounding the design of problems seems to have received little attention. Thus research on PBL problem design is rather scarce and unsystematic. To provide PBL educators with a systematic conceptual framework for designing PBL problems, Hung (2006) introduced the 3C3R model as a conceptual framework for systematically designing PBL problems. In current study, Computer Assisted Problem Based Learning (CAPBL) environment was designed in the subject of Endocrine System in Human Beings considering 3C3R model in high school biology by one of researcher. The aim of current study was to introduce a Computer Assisted Problem Based Learning (CAPBL) environment. (C) 2012 Published by Elsevier Ltd.