Individualized assessments of the effects of three doses of methylphenidate (MPH) were conducted for 2 students with attention deficit hyperactivity disorder within each child's classroom using behavioral, academic, and social measures. A double-blind, placebo-controlled, multielement design was used to evaluate the results. Results suggested that at least one or more dosages of MPH were associated with some degree of improvement for both children in each area of functioning as compared to placebo. However, the degree of improvement at times varied substantially across dosage and area of functioning. Results suggest that MPH dosage and area of child functioning are critical assessment parameters and that controlled clinical trials are necessary to optimize the effectiveness of treatment with MPH for the individual child.DESCRIPTORS: attention deficit hyperactivity disorder, methylphenidate, behavioral assessment, behavioral pharmacology Methylphenidate (MPH) is often effective for the management of a variety of classroom behaviors associated with attention deficit hyperactivity disorder (ADHD; e.g., Pelham, Bender, Caddell, Booth, & Moorer, 1985;Rapport, Murphy, & Bailey, 1982). However, children are often placed on MPH with little or no objective evaluation of medication effects. In addition, a determination of the effects of MPH for an individual child is complicated by several factors. First, individual differences in response to methylphenidate appear to be the rule rather than the exception (Pelham et al., 1993). Second, dose-response relations for an individual child may be linear (continued improvement with increasing dose) or quadratic (improvement to a peak effect followed by a decrePortions of this paper served as partial fulfillment for the first author's Master of Arts degree from Louisiana State University. We would like to thank the participating children and their families, the supervising physicians, Stephanie Edwards, Jennifer Gaines, and Iantha Fusilier.Requests for reprints should be sent to Veronica Gulley, Department of Psychology, 236 Audubon Hall, Louisiana State University, Baton Rouge, Louisiana 70803. ment in performance), or reach a therapeutic threshold (improvement followed by no further change with increasing dose; DuPaul & Barkley, 1993). Thus, both overall effectiveness and an optimal dose may be very different for otherwise similar children. Finally, there is some evidence that response to MPH may vary within children across behavioral, academic, and social areas of functioning, both at the same and at different dosages (Forness, Swanson, Cantwell, Guthrie, & Sena, 1992;Sprague & Sleator, 1977).The above literature suggests a number of limitations to previous evaluations of the effects of MPH. First, an overwhelming majority of studies have evaluated treatment effects based on subjective parent report, teacher report, and behavior rating scales. Unfortunately, these procedures are subject to informant bias and are often technically inadequate (Stoner, Carey, Ikeda, & Shinn, 1994...