In children with attention deficit hyperactivity disorder (ADHD), the effects of methylphenidate were investigated in a pharmacodynamic comparison of placebo and the standard b.i.d. administration of methylphenidate. In each of these conditions, teachers completed ratings in classroom settings at times chosen to coincide with expected "peaks" and "troughs" of serum concentrations in the b.i.d. condition. Analyses of variance (ANOVAs) revealed the expected differences between the two conditions in the laboratory classroom setting using standard rating scales (Conners and the IOWA Conners) and a new rating scale (the SKAMP), which specifically measures the classroom manifestation of ADHD. The psychometric properties of the SKAMP were evaluated by calculating test-retest reliability and by calculating correlations with the standard rating scales to establish concurrent validity.