Clinicians frequently describe incomplete adherence to stimulant medication as a limitation to the effectiveness of treating ADHD in adolescents. This study examined reported adherence among 44 adolescents prescribed medication for symptoms of attention deficit hyperactivity disorder (ADHD). Reports of medication adherence were obtained from adolescents and parents at two time points, approximately two months apart. Parent and adolescent reports indicated reasonable agreement, with parents and adolescents reporting high rates of adherence at both time points (medians ranged from 85 to 89% adherence). A small group of adolescents reported extremely low rates of adherence, but we were not able to distinguish this group from the remainder of the sample based on demographics. It is argued that the sample is generally representative of adolescents who are being prescribed medication for ADHD, and that the high adherence rates are valid. These findings imply that clinicians treating adolescents with ADHD should be cautious in assuming that medication adherence is all inevitable problem in this population.