The purpose of the present research was to show how social identity theory can be applied to enhance individual productivity within groups. Three experiments manipulated in-group identifiability and importance of the group for one's social identity, and compared individual's productivity when working alone to when working in a group setting. The group setting in the first study involved either a collective of unrelated individuals, a group of participants expecting future interaction, or a group working for a group reward. The second study compared productivity in groups with four differing interdependent reward structures. The final study examine the impact of group members wearing a common uniform (vs. no uniform) and the presence (or absence) of an out-group. Results supported the general prediction that group productivity would be enhanced by factors that increase group categorization and the importance of the group to members' social identities (future interaction, interdependent reward structure and uniform/out-group present). However, productivity in groups was not influenced by perceptions of the task or identifiability of performance. These findings extend social identity theory by suggesting that group members will increase their in-group position through individual work efforts.