Boys between the ages of 9 and 10 participated in one of three experimental activities. One involved movement and aggression, the second movement devoid of aggression, and the third minimal movement of a nonaggressive nature. Aggressive fantasy decreased in the aggressive movement and minimal movement groups but increased in the nonaggressive movement group. The results are consistent with a cathartic view of the functional relationship between aggressive behavior and aggressive fantasy when the effects of movement and completion of an aggressive response are considered. This study supports the notion that the enactment of an aggressive goal response is essential to the occurrence of a cathartic effect and points up the importance of controlling for movement in investigations of the relationship between aggressive fantasy and aggressive behavior. An additional, exploratory investigation of daydreaming suggests that children who are high in aggressive fantasy are likely to daydream more frequently than children low in aggressive fantasy.