A significant body of research identifies a large number of team composition characteristics that affect the success of individuals and teams in cooperative learning and project-based team environments. Controlling these factors when assigning students to teams should result in improved learning experiences. However, it is very difficult for instructors to consider more than a few criteria when assigning teams, particularly in large classes. As a result, most instructors allow students to self-select teams, randomly assign teams, or, at best, balance teams on a very limited number of criteria. This paper describes the design of Team-Maker, a web-based software tool that surveys students about criteria that instructors want to use when creating teams and determines optimal team assignments based on the distribution criteria that instructors specify. The Team-Maker system was validated by comparing the team assignments generated by the Team-Maker software to assignments made by an experienced faculty member using the same criteria. This validation experiment showed that Team-Maker consistently met the specified criteria more closely than the faculty member. We suggest that Team-Maker can be used in combination withthe Comprehensive Assessment of Team-Member Effectiveness (CATME) peer evaluation 2 instrument to form a powerful faculty support system for team-based and cooperative learning and for a variety of research purposes. Internet access to both the Team-Maker and CATME systems is freely available to college faculty in all disciplines by selecting the “request faculty account” button at www.catme.org.