This article investigates geographic variation in stimulant medication use by youth with attention-deficit/hyperactivity disorder (ADHD) served by public mental health and/or drug and alcohol programs in San Diego (n = 790) during 1997-1998 and in Puerto Rico (n = 726) during 1998. Youth were stratified into four groups: (a) ADHD, (b) ADHD--not otherwise specified (ADHD-NOS), (c) other "DSM-IV" diagnoses, (d) no diagnosis. Reported rates of stimulant use were as follows: ADHD, 32.9% (Puerto Rico) and 38.8% (San Diego), and ADHD-NOS, 20.2% (Puerto Rico) and 17.8% (San Diego). Youth in San Diego were more likely to use other psychotropics and to have experienced residential or inpatient care compared with youth in Puerto Rico. A regression model indicated that predictors of stimulant use at both sites included ADHD, ADHD-NOS, male gender, and younger age. Despite sociodemographic and cultural differences, both settings demonstrated similar patterns of stimulant use, suggesting these medications are not overused in public sectors.