The current study used a microworld simulation to investigate the direction of the relationship between group cohesiveness and performance. The study involved ten 4-person teams who undertook 12 sessions of an air traffic control simulation. Performance and cohesiveness data were collected at each 1-hr session. Using hierarchical linear modeling, group performance was found to predict group cohesiveness and not vice-versa. These findings are discussed with respect to previous research and popular theories of group development.