The amounts of endogenous fat and fatty acids in growing pigs were determined in digesta from the terminal ileum and in faeces. Graded levels of soybean oil were added to a diet poor in fat, and the endogenous fat secretion was estimated by the regression method. Both in ileal digesta and faecal material low concentrations of fatty acids were found in the extracted fat. The digestibility of fat as well as fatty acids increased when adding fat to the diets, indicating a strong influence of endogenous lipids. The amount of endogenous fat determined at ileum level or in faeces was calculated to be 4.7 and 4.4 g, respectively, per kg dietary DM intake. Although the values were low compared with other published data they correspond to about 10% of the fat intake from a standard Danish grower diet. The amount of endogenous saturated fatty acids in faeces was higher than that of unsaturated but lower than at the terminal ileum level, suggesting microbial hydrogenation of unsaturated fatty acids in the hindgut. The dominating fatty acids at terminal ileum contributed about 2% of dietary fatty acids when pigs were fed a standard Danish diet.