['We examined how well waist circumference (WC) reflects total and abdominal fat and whether WC predicts insulin resistance independent of body mass index (BMI) percentile in youths.', 'Body composition was measured by dual-energy x-ray absorptiometry and abdominal adiposity by computed tomography. Insulin sensitivity was measured by the hyperinsulinemic-euglycemic clamp.', 'Both BMI percentile and WC were significantly associated (P < .01) with total and abdominal fat and insulin sensitivity. WC remained a significant (P < .01) correlate of total and abdominal fat and insulin sensitivity after controlling for BMI percentile. By contrast, BMI percentile did not remain a significant correlate of visceral fat and markers of insulin resistance after controlling for WC. Without exception, WC explained a greater variance in abdominal fat and metabolic profiles than did BMI percentile.'] Is waist circumference an independent predictor of insulin resistance in black and white youths?