- To examine the social effects of methylphenidate, groups of 15 attention-deficit disordered boys with (ADD) and 15 ADD boys without conduct problems (ADD/CP) were paired with normal peers. ADD and ADD/CP children showed a different pattern of responses to methylphenidate. While on task behavior in ADD/CP dyads increased at 0.15 mg/kg doses, increases in ADD dyads were not observed until doses reached 0.50 mg/kg. Although controlling interaction in ADD children decreased at 0.15 mg/kg, the controlling behavior of ADD/CP children did not decline at either dose. Peers of both ADD and ADD/CP children showed reciprocal declines in controlling behavior. In both free play and cooperative task situations, 0.15 mg/kg increased social interaction in ADD boys and decreased social interaction in ADD/CP boys.