Methylphenidate and amphetamines are considered to be the first line of treatment for ADHD in children (Biederman et al, 1997). Although treating children and adolescents with stimulants does not appear to increase the risk of substance use disorders (Wilens et al, 2003), little is known about the abuse of prescription stimulants in adults with ADHD. A review of the literature on the abuse potential of methylphenidate in animals and humans found that methylphenidate produced reinforcing, discriminative-stimulus, and subjective effects similar to amphetamines or cocaine (Kollins et al, 2001). Although the abuse rates of methylphenidate and other stimulant medications used for the treatment of ADHD have not been empirically established, significant concern exists so that regulatory mandates are enforced to control distribution, and some physicians may be reluctant to use stimulants in patients with drug abuse histories. The introduction of a methylphenidate patch is an important advancement, as the patch formulation should increase compliance while minimizing abuse potential, making it an attractive treatment option in the large population of individuals who have a history of previous drug misuse. The primary aim of this study is to assess the efficacy of the methylphenidate patch in adult individuals with ADHD who have abused stimulants in the past. It is hypothesized that the methylphenidate patch will be efficacious in reducing ADHD symptoms in this population.