Web-based collaborative Problem-Based Learning (PBL) environments have great potential for learner improvement in solving ill-structured problems in practical situations. Web-based environments, however, offer learners relatively few chances to solve problems through face-to-face interactions compared to traditional classrooms, thereby making it difficult for learners to develop a shared understanding for particular mutual task performances. Therefore, academic efforts are needed to overcome this limitation. As one such effort, this study suggests the use of Collaborative Representation Supporting Tool (CRST), which is newly developed to support learners in constructing their shared knowledge structures collaboratively. This visibly persistent tool may effectively lead people toward more focused discourses by providing them with the means to externalize their emerging knowledge. As a result of providing the CRST, the conclusion could be made that this tool was highly beneficial for learners. In PBL processes as well as PBL outcomes, the use of the CRST had more positive effects statistically than the use of a web bulletin board without the CRST. The results of this study suggest that the CRST can be a helpful tool to support collaborative learning in web-based collaborative PBL environments. (Contains 8 tables and 6 figures.)