Specimens from one case each of acquired and congenital cutis laxa were examined by electron microscopy. Elastic flbers of the dermis and subcutaneous arteries and veins were found to have similar changes. Elastin was diminished and microfilaments were visible throughout the entire fiber. Electron-dense, amorphous or granular layers that alternate with relatively electron-light layers were deficient. This electron-dense substance was unevenly aggregated within or in the vicinity of elastic fiber. In the congenital case, the aggregation and deposition fo the electron-dense substance was often pronounced. In the vein, deficient deposition of elastin and admixture of microfilaments and amorphous substance were also found. Such admixture was often encircled by fibroblasts or smooth muscle cells. In the artery, multiplication of basal lamina was seen. Collagen fibers and anchoring fibrils of the skin were normal.