In an experimental study involving power differences between groups, the effects of legitimate and illegitimate explanations for power were investigated on measures of affect, stereotyping, and memory. We found that powerless groups reported more positive affect (relative to negative affect) when explanations were provided for their powerlessness, whether these explanations were legitimate or illegitimate. In addition, members of powerless groups attributed greater intelligence and responsibility to the outgroup when it was in a position of high power rather than equal power; again, these effects on stereotyping were enhanced when explanations for the power differences were provided. Finally, research participants tended to mis-remember the reasons given for the power differences as more legitimate than they actually were. These results support a system justification theory of intergroup behavior (Jost & Banaji, 1994) in that people seem to imbue placebic explanations with legitimacy, use stereotypes to rationalize power differences, and exhibit biases in memory such that the status quo is increasingly legitimized over time.