AbstractThe enzymes elastase, chymotrypsin, pepsin, pronase, hyaluronidase, and collagenase were utilized on thin Epon sections to obtain further information on the nature of elastic fibers. Results showed that the central amorphous material was selectively removed by elastase and after hydrogen peroxide pretreatment it also was removed by chymotrypsin, pepsin and pronase. None of the enzymes removed the peripheral microfibrils, but pepsin did accentuate the density and periodic beading of these structures. The failure of proteases to remove the microfibrils under these conditions is discussed.