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Background: Subcutaneous fat measurements have been recently found to show sex differences in variability (dispersion dimorphism) in young adult samples from two extant unrelated European populations, with males more variable than females., Aim: This paper aims to investigate potential sex-by-age interaction and to verify its presence and possible different expression in various populations., Subjects and Methods: Biceps, triceps, subscapular, suprailiac, abdominal, midthigh and calf skinfolds were analysed in two European samples from the Basque Country (4176 subjects, 8-50 years) and from Sardinia (2491 subjects, 14-100 years). Data on triceps and subscapular skinfolds in Non-Hispanic Whites (1799 subjects, 8-75 years), Mexican Americans (3133 subjects, 8-85 years), Other samples (1733 subjects, 8-70 years) from NHANES (2001-2002) were also included in the analysis. The significance of the difference between male and female coefficients of variation was performed by means of a suitable non-parametric bootstrap test., Results: Skinfold coefficients of variation were greater in males than in females in 79.8% of comparisons with 27.2% significant differences. Dispersion dimorphism was particularly evident in peripheral subcutaneous fat depots. The results do not show appreciable variations across population samples and age classes., Conclusion: Skinfold dispersion dimorphism seems to exist throughout most of the life cycle, and be widespread in European and non-European human populations. It involves especially accumulation sites of the gynoid pattern known to be relevant in female reproduction. More 'standardized' fatty reserves in women might represent a selective advantage. On the other hand, skinfold dispersion dimorphism might also be related to cultural factors affecting the extent of female variability by means of enhanced environmental homogeneity.