INTRODUCTION: The data of four growth studies involving populations from Andalusia, Barcelona, Bilbao and Zaragoza have recently been reported as part of the Spanish Cross-sectional Growth Study 2008 (SCGS). With the aim of detecting possible differences between the population of the Madrid region and those of the SCGS, and by so-doing assess the applicability of the conclusions of this reference work to the Madrid region, a cross-sectional study of the latter was undertaken, recording the weight, height and body mass index (BMI). SUBJECTS AND METHODS: We have analyzed 6463 subjects (3055 females and 3408 males) aged 3-24 years. All subjects were healthy, Caucasian, and of Spanish origin. Differences between the results of the Madrid and SCGS studies were sought by multiple linear regression analysis of the log of the height, weight and BMI data adjusted for age and geographical area. The Tukey multiple comparisons test was used to analyse differences in age ranges. All calculations were performed using SAS v. 8.2 software. RESULTS: Means and standard deviations are provided for the weight, height and BMI of women and men; distributions by percentiles are also provided. No differences of clinical importance were seen in the weight, height or BMI between the subjects of the Madrid region and those of the SCGS. However, comparisons with the results of other studies performed more than 20 years ago revealed an increase in the weight and height values in all percentiles. CONCLUSIONS: In summary, the official Spanish SCGS reference data for 2008 are similar to those recorded for the Madrid region. Bearing in mind that recent cross-sectional studies undertaken in Andalusia, Aragon, Catalonia, the Basque Country and the present work show no significant differences in mean weights, heights or BMIs in any age group, nor in the final height attained by adults, the Spanish population would appear to be anthropometrically homogeneous. The conclusions of the SCGS may therefore be applicable to the entire country.