This study compared measures of sleep from an accelerometer worn on the hip to measures obtained from an accelerometer worn on the wrist, the gold standard measure of sleep behavior in community research. The accelerometer worn on the hip provides a measure of total sleep time in 10- to 11-year-old children comparable to the wrist-worn unit. We provide an alternate method to ascertain bedtime and final wake time when diary data are missing. A hip-worn accelerometer may provide a cost-effective means of gathering physical activity and sleep data simultaneously in large samples of children with or without an accompanying sleep diary.