Gastrointestinal lipid digestion consists of three sequential steps:(0) the dispersion of bulk fat globules into finely divided emulsion particles,(b) the enzymatic hydrolysis of fatty acid esters at the emulsion-water interface, and (c) the desorption and dispersion of insoluble lipid products into an absorbable form. Here we emphasize several newer aspects of the biochem istry and biophysics of lipid digestion and absorption. We review the physi cal-chemical behavior of dietary lipids in model systems and correlate this information with their physiological behavior throughout the alimentary canal.