Discusses the diagnosis and treatment of attention deficit hyperactivity disorder (ADHD) in a men's prison by evaluating a group of inmates who completed a program developed by the author. The characteristics of ADHD, such as distractibility, poor attending, impulsive behavior and resulting poor recall of consequences and poor judgement, may explain many impulsive crimes. The study groups consisted of 15-20 men, and follow-up visits were conducted to assess the effectiveness of Ritalin therapy. The most important component of the program is the ADHD training group, which included skills training in communication and expression of feelings. Results indicate that accurate diagnosis, careful training, and judicious use of appropriate medications could offer focus, social awareness, and the ability to "learn how to learn" in this group of patients. The justification for considering medical treatment and concerns regarding use of medication in prison are discussed. Common medications that are used are listed, and drug therapy for obsessive-compulsive behavior and bipolar disorder is examined. Unexpected results of the program include the education of correction officers and the realization of the challenge of prison medicine. Differential diagnoses are discussed, as well as the hidden costs of missed diagnoses. (PsycINFO Database Record (c) 2019 APA, all rights reserved)