The ability of relative body weight and triceps skinfold thickness to indicate obesity in adolescents was analyzed in 169 males and 66 females, 12-17 years of age, whose percent body fat had been determined by underwater weighing. Using 25% body fat in males and 30% in females as the criterion for obesity, 31 males and 17 females were placed in this category. Of these, the triceps skinfold correctly identified 15 males and 4 females, and the relative weight identified 16 and 5, respectively. These anthropometric indicators, at the levels applied, are low in sensitivity (23-50%) but high in specificity (85-100%).