Studied the effects of reward magnitude and comparability of the outgroup on minimal intergroup discrimination where self-interest was related to ingroup profit. Favouritism towards own group is hypothesized to arise from intergroup comparisons to enhance self-esteem as well as instrumental rivalry for group and self-interest. Sixty-two fourteen to fifteen years' old school-boys and girls were randomly assigned to a high or low reward condition in which they distributed monetary rewards, via choice-matrices, to the ingroup and a relevant comparison outgroup, and the ingroup and an irrelevant comparison outgroup. Monetary self-interest was explicitly and directly linked to ingroup's absolute profit. Ss sacrificed group and personal gain to achieve intergroup differences in monetary outcomes favouring the ingroup; and were less fair and more discriminatory towards the relevant than irrelevant outgroup. especially with High Rewards.