AbstractA series of experiments utilizing the technique of Rostgaard and Barrnett which purported to demonstrate lead‐lipid complexes was performed to study the efficacy of using lead as a marker in lipid absorption.The jejunal mucosa from adult cats fasted 48 hours and fed corn oil by stomach tube was fixed in buffered glutaraldehyde for two hours, washed in cacodylate buffer and then incubated for 20 minutes in tris‐maleate buffer (pH 7.2) which contained 4mM of lead nitrate. Following osmication, dehydration and embedding in Epon, thin sections, either stained or unstained were examined in an electron microscope. Lead deposits of varying size were observed in, on and about the microvilli. In addition, lead deposits were observed related to mucous cells. The jejunal mucosa of cats fasted 48 hours and fed 5% dextrose and treated as the lipid‐fed animals gave similar results. Fasted animals had few lead deposits related to the gut epithelium.When jejunal mucosa from lipid‐ or carbohydrate‐fed animals was extracted in lipid solvents prior to incubation in tris‐maleate containing 4mM of lead nitrate, the lead densities persisted.In view of the foregoing, the occurrence of lead precipitates following a fatty meal does not offer an unequivocal means of tracing lipid absorption in the smal