The three-dimensional cytoarchitecture of normal and atherosclerotic intima of human aorta was studied by light microscopy of consecutive en face preparations (Hautchen preparations) and by scanning electron microscopy. In unaffected intima, a three-dimensional network consisting of cells of variable shape and probably origin was demonstrated. Cellular shape changed from predominantly stellate in the luminal regions of the elastic-hyperplastic layer to elongated spindlelike cells in the musculoelastic layer of the intima. In the surface layers of the fatty streak, cellular contacts were severed, and lipid droplets were often seen between cellular processes. Along with stellate and elongated cells, the fatty streak also had a number of round monocytelike cells. Lipid inclusions were usually detected in stellate and ovoid cells. The integrity of the cellular network was preserved at the marginal zone of the atherosclerotic plaque, while at the slopes and in the central part of the plaque, cells practically lost all contact with each other. Giant stellate cells embedded in crude fibrillar connective tissue matrix were often found there. Disintegration of the cellular network during atherosclerosis is suggested to play an important role in the development of various lesions.