Body mass index (BMI) as a predictor of slipped capital femoral epiphysis (SCFE) was studied. A total of 26 adolescent patients had complete annual height and weight measurements taken from birth to onset of slippage. These values were compared with those of the normal adolescent population. Patients with SCFE showed statistically higher BMI during growth than normal developing children. BMI gives more accurate data on body build than height and weight alone and may be a useful tool for evaluating risk factors in SCFE.