Objective:To determine reference values for body mass index (BMI), sum of six skinfolds (∑6 skinfolds) and body fat percentage (BF%) in Spanish adolescents aged 13–18 years, included in the AVENA Study (Alimentación y Valoración del Estado Nutricional en Adolescentes: Food and Assessment of the Nutritional Status of Adolescents).Design:Multicentre cross-sectional study.Setting:Representative sample of Spanish adolescents.Subjects:The population was selected by means of a multiplestep, simple random sampling. The final number of subjects included in the AVENA Study was 2859 adolescents; 2160 adolescents had a complete set of anthropometric measurements and were then included in this study (1109 males and 1051 females).Interventions:Weight, height and six skinfold thicknesses were measured. As indices of total adiposity, we calculated BMI, ∑6 skinfolds and BF% with the formulas described by Slaughter et al.Results:∑6 skinfolds and BF% in each age group were significantly higher in females than in males. In males, age showed a significant effect for BMI, ∑6 skinfolds and BF%; however, in females, the effect was only significant for BF%. The percentile distribution was more disperse towards higher ∑6 skinfolds and BF% values in males when compared with females.Conclusions:The presented percentile values will help us to classify adolescents in comparison with a well-established reference population, and to estimate the proportion of adolescents with high or low adiposity amounts.Sponsorship:The AVENA-Study was supported by the Spanish Ministry of Health (FIS 00/0015), and grants from Panrico SA, Madaus SA and Procter and Gamble SA. This study was also supported by Instituto de Salud Carlos III (Spain), RCESP (C03/09) and Spanish Ministry of Education (AP2003-2128).