The behavioral constructs that emerge from observers' open-ended impressions of methylphenidate effects on the social behaviors of hyperactive children were examined. Ninety-six undergraduates observed videotapes of two different hyperactive "target" boys, each playing an interaction game with three peers. One target was taking methylphenidate and the other was taking placebo. The valence and content of observers' social perceptions were analyzed. Overall, more negative than positive behaviors were detected, a pattern more pronounced for the placebo than for the medication condition. Interestingly, placebo targets received negative evaluations for poorly controlled behaviors such as noncompliance, aggression, and disruption, but medicated targets received negative evaluations for social inhibition--passive and submissive behaviors. In contrast, the boys' medication state did not consistently influence observers' perceptions of positive social behaviors. Discussion focused on the extent and consequences of medication-related increases in social disengagement and on the ultimate impact of stimulant treatment on hyperactive children's social worlds.