the purpose o f the present study was to investigate the effect o f group goal difficulty and group goal commitment on group performance. in addition, it was also to investigate two mediating processes, effort and cooperation, using weldon and weingart’s (1993) model o f group goals and group performance in the sport and motor domain. twenty-four groups o f three people each performed a 2-minute triangle basketball passing task. the groups were randomly assigned to two different goal conditions: easy goals or hard goals. the design was a 2 (goal conditions) x 2 (pre/posttest) mixed factorial with repeated measures on the last factor. performance results indicated a significant goal condition by test interaction effect. the post hoc analysis showed that the hard goal groups exhibited significantly more improvement than the easy goal groups. no significant differences were found for goal commitment, effort, or cooperation. results are discussed in terms of weldon and weingart’s model and locke and latham’s goal setting theory as well as some recent research about goal setting in sport setting.