Research has shown the potential of a problem-based approach to enhance students' learning. The interactive nature of hypermedia technology and its ability to deliver information in different media formats can provide unique capabilities for implementing problem-based learning (PBL) environments. Yet, little is known about the types of tools that are effective in supporting learning in hypermedia supported PBL environments. The purpose of this exploratory study is to investigate both the use of tools and design features in a piece of PBL software and their effectiveness on middle school students' learning. Specifically, the following research questions formed the focus of the study: Do any navigational profiles emerge among the student teams? If so, how do they compare usage of the tools embedded in the PBL environment? If navigational profiles exist, how do they compare in terms of the external criteria such as science aptitude, recall and transfer measures, and attitude toward the environment? If navigational profiles do not exist, what is the relationship between tool use and student achievement and attitude? (Contains 15 references.) (AEF)