In this study we conducted single-case analyses of the dosage and time-course effects of methylphenidate (MPH; Ritalin) on disruptive classroom behavior, math and reading performance, and social engagement. Clear individual differences were demonstrated (a) across children; (b) across academic, behavioral, and social domains of functioning; (c) for dose-response effects; and (d) in the onset and duration of effects. These results are in contrast to the majority of group studies that suggest a generally positive and linear dose-response effect for MPH across both children and domains of functioning. No particular dose-response relationship between disruptive behavior and academic performance was indicated. However, an increasing dosage of MPH was associated with increasing social withdrawal for 2 of the 3 participants. Implications for school-based medication evaluations and for designing optimal comprehensive interventions for children who receive MPH are discussed.