Objective: To determine reference values for body mass index (BMI), sum of six skinfolds (Sigma 6 skinfolds) and body fat percentage (BF%) in Spanish adolescents aged 13-18 years, included in the AVENA Study (Alimentacion y Valoracion 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, Sigma 6 skinfolds and BF% with the formulas described by Slaughter et al. Results: Sigma 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 Sigma 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.