Adipose tissue fatty acid composition was studied in 139 boys, a subgroup of 1521 subjects aged 8-16 participating in the United States (New York City)--Greece cross-cultural study of coronary heart disease risk factor development. Adipose tissue was obtained by an aspiration technique, followed by transmethylation of fatty acids and gas-liquid chromatographic analysis. Statistically significant differences were found among different cohorts in their adipose tissue content of saturated, monounsaturated and polyunsaturated fatty acids. All United States cohorts had significantly higher (p less than 0.0001) levels of saturated and polyunsaturated fatty acids and significantly lower (p less than 0.0001) monounsaturated fatty acids compared to the Greece cohorts. These relationships held for all three types of fatty acids whether the non-Greek cohort from New York City or the cohorts of adolescents of Greek descent who reside in New York City alone, were compared to the cohorts residing in Greece. The differences in the adipose tissue fatty acids between the cohorts may be an important expression of the biochemical milieu which contributes to the development of relatively low coronary heart disease rates in Greece compared to those in the United States.