This study examined the effects of 0.3 mg/kg methylphenidate (MPH) and expectancy regarding medication on the performance and persistence of 137 boys with attention-deficit/hyperactivity disorder (ADHD) in a get-acquainted dyadic interaction with a peer, using a balanced-placebo design. Boys in 4 groups-administered placebo or MPH crossed with being told they received placebo or MPH-interacted with child confederates in experimental situations in which social success and failure were manipulated. In contrast with studies of academic persistence, MPH did not affect boys' task persistence or performance. Boys gave more positive self-evaluations and talked more in the success condition as compared with the failure condition. Boys attributed success to effort and ability and failure to task difficulty, and neither MPH nor expectancy affected this pattern. These findings are consistent with other studies in failing to find debilitating effects of MPH or medication expectancies on ADHD boys' attributions or self-evaluations.