In 2 experiments, 64 male students worked almost continuously for 20 hr without sleep under varying social conditions. In Experiment 1, participants worked either individually or as a group. As hypothesized, performance deteriorated over time, especially in the group condition, which allowed participants to loaf. In Experiment 2, all participants worked in groups. They were instructed that public feedback would be provided either on the group result only or on the individual results of all group members. As expected, when individual results were made public, performance deteriorated less. Overall, the data suggest that fatigue increases social loafing. However, both individualizing the task and providing public individual feedback seem to counteract these effects.