FTIR microscopy is a versatile technique successfully used to probe the subcellular chemical composition of atherosclerostic arterial walls. To design new vascular substitutes that resist lipid uptake (the major cause of the phenomenon referred to as atherosclerosis-like), identifying and understanding lipid distribution within the pseudoatherosclerosed arterial prostheses is of prime importance. Until now, the amount of lipids present within arterial prostheses that had been explanted from either animals (during in vivo trials) or humans (after the failure of vascular grafts) or had been submitted to in vitro investigations could only be measured through the use of histological techniques or radioactive labeling methods. We present here a novel method to quantitatively measure the lipid concentration profile within the wall of arterial prostheses by means of Fourier transform infrared microspectroscopy. Essentially, prostheses are fixed in a 1% osmium tetraoxide aqueous solution under vacuum and radially cut with a 5-micron thickness with a microtome. The sections are then placed onto BaF2 windows and observed with a microscope attached to a FTIR spectrometer with a 30 microns x 50 microns sampling area. The lipid concentration profile is obtained by scanning the prosthesis wall from the inner to the outer surface and reporting the corresponding integrated absorbance between 2700 and 3100 cm(-1) against a calibration curve. The application of this technique constitutes the first quantitative measurement of the concentration of biological molecules within the wall of artificial arterial substitute.