Obesity in children and adolescents is a growing epidemic in the United States, and physicians are increasingly looking for safe and effective treatments. In recent years, pharmacologic treatment has been considered for severe and refractory cases of adolescent obesity. We present a case of an obese adolescent who presented to an inpatient psychiatric unit with a body mass index (BMI) of 37.8 (>98th percentile for age). He was started on zonisamide for the purposes of weight loss, and a steady decrease in weight and BMI was noted through 4 months of outpatient follow-up. During this time, the patient's weight decreased from 126.8 kg to 106.2 kg, a 20.6-kg loss, representing a 16.25% reduction in weight. His most recent BMI decreased to 31.7 (96th percentile for age). We discuss the potential use of zonisamide for weight loss in adolescents, considering the potential risks and benefits.INDEX TERMS adolescents, antiobesity agents, obesity, weight loss, zonisamide J Pediatr Pharmacol Ther 2013;18(4):311-314