Mice maintained on a high fat/high cholesterol diet were fed a similar high fat/high cholesterol diet for 4 days that also contained the non-absorbable marker sucrose polybehenate as 5% of the dietary fat. Fecal samples were collected daily. Fatty acids present in the original diet as well as the feces were derivatized to their respective methyl esters and quantified by gas chromatography. Fat absorption was calculated from the ratios of behenic acid to other fatty acids in the diet versus the feces. Two experiments were averaged for n = 6 wild type (WT), n =7 PTL−/−, n = 8 CEL−/− and n = 7 PTL−/−,CEL−/− mice and shown as the means ± S.E. for each genotype. *, p < 0.05; ***, p < 0.001 (differences from wild type mice).