A double-blind, placebo-controlled study was used to investigate the effects of methylphenidate (Ritalin) on tests of auditory processing in children diagnosed with both Attention Deficit Hyperactivity Disorder (ADHD) and Central Auditory Processing Disorder (CAPD). Thirty-two subjects received three Central Auditory Processing (CAP) tests and the Auditory Continuous Performance Test (ACPT), a measure of attention/impulsivity, at two separate test sessions: once when medicated with Ritalin and once when nonmedicated (placebo). Sixteen subjects were assigned randomly to receive their medication first and 16 to receive the placebo first. A counterbalanced 2 x 2 mixed factorial analysis of variance was conducted for each of the four dependent variables: Staggered Spondaic Word (SSW), Phonemic Synthesis (PS), Speech-in-Noise (SN), and ACPT measures. Analyses revealed that Ritalin did not have a significant effect on any of the three CAP measures. However, ACPT performance was significantly better (p < .000) for the Ritalin versus placebo condition.