The purpose of this study was to determine the ability of air displacement plethysmography (ADP) to estimate body fatness in prepubertal and early pubertal African American and white children. One hundred nineteen nonoverweight and overweight boys (N ϭ 56) and girls (N ϭ 63), age (mean Ϯ SD) 9.8 Ϯ 1.7 y, body mass index 25.9 Ϯ 7.6 kg/m 2 (range, 14.2-47.0 kg/m 2 ), and mean percent body fat (%BF) by dual-energy x-ray absorptiometry (DXA) 39.2 Ϯ 11.7% (range, 12.2-57.5%), were studied. %BF by ADP was compared with DXA %BF estimates and with body fat by several field methods: skinfold thicknesses using the Slaughter et al. equations (Hum Biol 60: 709 -723, 1988), bioelectrical impedance analysis (BIA) using the Houtkooper et al. equation (J Appl Physiol 72: 366 -373, 1992), and a predictive equation using skinfold thicknesses, BIA, and weight (Goran et al.: Am J Clin Nutr 63: 299 -305, 1996). All methods used to estimate %BF were significantly correlated with DXA (all p Ͻ 0.0001), with r 2 ranging from 0.85 (skinfold measurements) to 0.95 (ADP). ADP using the Siri equation underestimated %BF by Ϫ1.9% (p Ͻ 0.001); the Bland-Altman limits of agreement (defined as Ϯ2 SD) were Ϯ7.4%. %BF by ADP-Siri underestimated %BF by DXA by 3.0% for girls (p Ͻ 0.001) and by 0.6% for boys (NS). Agreement between body fat estimation by ADP and DXA did not vary with age, race, or pubertal stage. Application of the age-adjusted Lohman model to ADP significantly increased the magnitude of the underestimation to Ϫ6.9% (p Ͻ 0.0001). Prediction of %BF by the Slaughter skinfold thickness equation showed no significant mean bias for the overall data, but significantly underestimated %BF in girls (Ϫ3.7%) while overestimating %BF in boys (ϩ2.4%) with wide limits of agreement (Ϯ17.7%, p Ͻ 0.01 versus ADP). %BF by the Houtkooper BIA equation or Goran model underestimated %BF to a significantly greater degree than ADP (Houtkooper, Ϫ8.1%; Goran, Ϫ10.1%; both p Ͻ 0.0001 versus DXA or ADP). Determination of %BF from ADP using the Siri model slightly underestimates %BF as determined by DXA in girls, but appears to be superior to existing field methods both in accuracy and limits of agreement. Because of the ease with which it can be performed, ADP may prove useful for investigations of adiposity in children. Excessive body weight has become increasingly common among children in the United States (1). The prevalence of overweight in children and adolescents has almost doubled during the past two decades, and is now approximately 14% of young children and 12% of adolescents (2, 3).Accurate assessment of body composition, particularly body fatness, is a key component for both research about and clinical treatment of childhood obesity. Assessing body fatness and changes in body adiposity while children are growing can be difficult, because of the confounding effects of growth on lean and fat mass. Several different methods for estimation of body fat mass have been developed that depend on measurements of total body water, total body potassium, x-ray ab...

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