The goal of this study was to gain insights into the interactions that occur in online communications in a project-based learning activity implemented in an undergraduate course. A multi-case study was conducted of six collaborative groups, focusing on the types and frequencies of interactions that occurred within each group and the perceptions that students had of their experiences in this type of learning environment. It was found that the interactions within each group closely followed established steps in the problem solving process. The findings of this study go further in explaining specific indicators that may determine how well a group performs when using CMC as a support mechanism for project-based learning. High achievers tend to start early, are consistent in the frequency and extent to which they post messages, develop a sense of camaraderie online, are effective organizers and coordinators within the online environment, and engage in a deep, rich thought provoking dialog with a high degree of idea exchange. Low achievers on the other hand are slow starters, are erratic and inconsistent in posting messages, do not form bonds online, are not effective in organizing and accomplishing tasks online, and engage in shallow, directive dialog with little questioning and exchange of ideas. Students also differentiated between asynchronous and synchronous systems as to the type of tasks that are best suited for each. There was a general consensus that asynchronous system are best for tasks that require reflection, time, and deeper thought and synchronous systems are better for brainstorming, as a forum for the free flow of ideas, and for building group solidarity and social connection. (Contains 2 tables and 7 figures.)