A retrospective cohort study was conducted to evaluate the Department of Defense practice of allowing some individuals with a history of attention-deficit/hyperactivity disorder (ADHD) to enter military service (waiving for ADHD). Enlisted recruits who entered active duty with a waiver for academic problems related to ADHD were compared with control subjects who did not reveal health problems before entry, in terms of retention, promotion, and mental health-related outcomes. A total of 539 recruits with a history of ADHD were retained at the same rate as 1,617 control subjects, with no differences in promotion rates, comorbid diagnoses, or mental health-related discharges. On the basis of these findings, the Department of Defense medical accession standards have been changed to allow applicants who reveal a history of ADHD but did not require medication to finish high school or to hold a job for at least 1 year the opportunity to enter active duty without going through the current waiver process.