OBJECTIVE To determine whether intra-abdominal adipose tissue differs from subcutaneous adipose tissue in fatty acid content. METHODS Cross-sectional study of patients undergoing exploratory laparotomy, with adipose tissue sampling from subcutaneous, omental, mesenteric and retroperitoneal sites. METHODS Nineteen subjects, 8 men and 11 women, with a mean age of 64 (range 39-80), mean weight 78.9 kg (range 51-157) and mean body mass index of 27.5 (range 19.2-51.4). Fourteen of the 19 were undergoing surgery for colorectal cancer. METHODS Fatty acid content was assessed by gas chromatography and was compared between sites and between patients using general linear modeling. Spearman correlation coefficients were used to assess the association between subcutaneous and visceral adipose tissue. RESULTS For each of 17 fatty acids analyzed, there was a statistically significant difference in mean fatty acid values across individuals (p < 0.001). For seven of the fatty acids, there was a borderline or significant difference in mean fatty acid values across site, but there was no consistent pattern for one site differing from the others. Subcutaneous adipose tissue fatty acid content was highly correlated to visceral adipose tissue for saturated, unsaturated and trans fatty acids (p < 0.05 for 13 of 17 fatty acids). Variability across individuals was much greater than across site. The total explained variability (R2) for each fatty acid ranged between 49 and 93%, with the vast majority contributed by differences between individuals. CONCLUSION. Fatty acid content of subcutaneous abdominal adipose tissue is a good approximation of visceral adipose tissue. Because variability in fatty acid content is much larger between individuals than within a single individual across sites, subcutaneous abdominal adipose tissue fatty acid content can be used as a distinguishing characteristic among human populations.