Objective: To examine the relationship between childhood obesity as measured b y body mass index (BMI) and longterm morbidity after an acute ankle sprain. Desi gn: Six-month prospective cohort study with follow-up telephone questionnaires at 6 weeks and 6 months. Setting: Cincinnati Children’s Hospital Medical Cente r emergency department. Patients: Children between the ages of 8 and 18 years wh o presented with a chief complaint of an acute ankle injury were enrolled in the study. Children with ankle fractures were excluded. Exposed children were defin ed as those with a BMI in the 85th or greater percentile for age. Nonexposed chi ldren were defined as those with a BMI in the less than 85th percentile for age. Main Outcome Measures: Persistent symptoms of pain, swelling, or weakness; pain during or after exercise; and recurrent ankle injury. Results: A total of 199 c hildren were enrolled. The exposed and nonexposed groups were similar in terms o f sex, age, and ethnicity. A total of 164 (93%) had complete followup at 6 mont hs. Six months after an ankle injury, children with a BMI in the 85th or greater percentile for age were more likely to sustain persistent symptoms (relative ri sk, 1.70; 95%confi-dence interval, 1.10-2.61). Conclusion: Overweight chil dren are more likely to have persistent symptoms 6 months after an acute ankle s prain. Objective: To examine the relationship between childhood obesity as measured by body mass index (BMI) and longterm morbidity after an acute ankle sprain. Desi gn: Six-month prospective cohort study with follow-up telephone questionnaires at 6 weeks and 6 months. Setting : Cincinnati Children’s Hospital Medical Cente r emergency department. Patients: Children between the ages of 8 and 18 years wh o presented with a chief complaint of an acute ankle injury were enrolled in the study. Children with ankle fractures were excluded. Exposed children were defin ed as those with a BMI in the 85th or greater percentile for age. Nonexposed chi ldren were defined as those with a BMI in the less than 85th percentile for age. Main Outcome Measures: Persistent symptoms of pain, swelling, or weakness; pain during or after exercise; and recurrent ankle injury. Results: A total of 199 c hildren were enrolled. The exposed and nonexposed groups were similar in terms of sex, age, and ethnicity. A total of Six (85) years after greater than 80 years of age (relative ri sk, 1.70; 95% confi- dence interval, 1.10-2.61). Conclusion: Overweight chil dren are more likely to have persistent symptoms 6 months after an acute ankle s prain.