Recent studies in various populations indicate that lack of sleep is one of the potential risk factors predisposing the youth to obesity. A sound sleep is required for a sound wakefulness and learning. Sleep deprivation is associated with overweight and obesity. To see the relationship of sleep duration and Body Mass Index (BMI) in adolescents. A cross sectional study was undertaken in six randomly selected private higher secondary schools of urban Pondicherry. Total 1545 students participated in study. Self administered questionnaire contained the information regarding age, sex, height, weight, sleeping time, wake up time etc. Mean age of the participants was 15.9 years (SD +0.74) and mean sleep duration was 7.0 hours (SD +1.1). Nearly one fifth participants were found to be overweight and obese. BMI differed significantly between boys and girls (p<0.001). Mean BMI was significantly different among three groups of sleep duration (Short Sleep, Medium Sleep, Long Sleep). There was a definite relationship between short sleep duration and obesity in the present study. © 2013 Elsevier B.V., All rights reserved.