Results indicated that 11 percent of the ADHD patients reported selling their medications compared to none of the patients in the control group. Of the ADHD patients who sold their medication, 83 percent met the criteria for conduct disorder (CD) and another 83 percent met the criteria for substance use disorder (SUD). All of the ADHD patients who sold their medication had either comorbid CD or SUD. The findings suggest that practitioners should closely monitor medication use in older adolescent and young adult ADHD patients with CD and/or SUD. Subjects were derived from the 10-year followup of an ongoing case-control family study of ADHD that has been described in previous publications. Ninety-eight subjects completed structured psychiatric interviews for diagnostic purposes and also completed a self-report questionnaire regarding medication use in subjects with ADHD (56 percent of sample) compared with control subjects (44 percent of sample) who were receiving medication for other purposes. Data analysis included Pearson chi-square tests and t-tests as well as logistic regression analysis. Additional research is warranted on the appropriate use of prescription stimulants and nonstimulants in high-risk groups. Table, references