This study describes associations between early-stage endometrial cancer and type of dietary fat consumed, based on (i) adipose tissue fatty acid content (a biomarker for dietary fat) and (ii) self-reported frequencies of selected high-fat foods. Because obesity may be associated with high dietary fat intake as well as endometrial cancer, a secondary objective is to determine whether the observed dietary associations are statistically independent of body composition, assessed as percent body fat. To achieve these aims, we examined 20 cases of endometrial cancer in remission and 20 community controls, all aged 55–64. Abdominal adipose tissue biopsies from cases contained significantly higher concentrations of saturated fatty acids of intermediate chain length (C12-C16), lower ratios of polyunsaturated to saturated fatty acids (P:S ratio), and lower concentrations of CI8 polyunsaturated as well as CI8 saturated fatty acids. These differences were independent of degree of adiposity measured in a whole body 40K counter and several measurements of regional fat distribution. In addition, each subject's consumption of 20 high-fat items was reported by means of a semiquantitative food frequency questionnaire. Analysis of these data indicated that cases consumed more animal-derived fats, again independent of obesity. In particular, cases used more butter in cooking, ate more bacon, and drank more whole milk. Animal-derived fat intake displayed an inverse association both with the P: S ratio and the C18 polyunsaturated fatty acid content of adipose tissue, lending internal validity to the dietary data. These findings are consistent with the hypothesis that the type of dietary fat consumed may influence the occurrence of endometrial cancer.