This work explores the psychological motives that shape the extent and nature of people’s cooperative behaviour in groups. In so doing, the authors bring together two literatures: the study of rule-following behaviour and the study of helping behaviour. They argue that both types of cooperative behaviour are rooted in people’s views about the justice of group procedures. Four components of procedures are shown largely to define people’s views about their fairness. Finally, the authors argue that people focus on procedural fairness because they use information about the fairness of group procedures to understand both the status of the group and their status within the group. These status judgments are important to people because they shape their self definitions and feelings of self worth.