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Obesity has become a public-health and policy problem in many parts of the world. Epidemiological and population studies in this field are usually based on different anthropometric measures; however, common genetic and environmental factors between these phenotypes have been scarcely studied. The objective of this article is to assess the strength of these factors on the covariation among a large set of obesity-related traits. The subject group consisted of 533 nuclear families living in the Greater Bilbao (Spain), and included 1,702 individuals aged 2-61 years. Detailed anthropometric measurements (stature, breadths, circumferences and skinfolds) were carried out in each subject. Bivariate quantitative genetic analyses were performed using a variance-components procedure implemented in the software SOLAR. The results revealed that the majority of these traits is affected by common genetic and environmental factors. All correlations were significantly different from 1 and varied from non-significant to very high (>0.90, P < 0.0001), with clearly lower pleiotropic effects among pairs including fat-distribution traits. Despite the strong common genetic effects detected among phenotypes determining the amount of body fat and mass, there is a residual genetic influence on the local fatness measures that cannot be explained exclusively by the genetic influence on overall fatness. Moreover, the observed relationships confirm a partially different genetic control of truncal and peripheral fat. In conclusion, our findings highlight the relevance of considering different types of traits in the prevention and treatment of obesity, as well as in the search for genes involved in its development.