A matrix game format was employed in a 2 × 2 design to study the effects of within group cooperation and competition under conditions of success and failure on subjects' subsequent treatment of own group and outgroup persons. Subjects in two-person groups either succeeded or failed at a cooperative or competitive game and then awarded points (worth money) to themselves, their partner, and two other people. A review of the relevant literature suggested that ingroup-outgroup bias would be greater after successful competition than after unsuccessful competition. The results supported this hypothesis. It was also found that subjects in the Cooperation-Failure condition displayed greater ingroup-outgroup bias than subjects in the Cooperation-Success condition. A qualification of the previous research supporting a positive relationship between group cohesiveness and ingroup-outgroup bias was suggested on the basis of the results.