A histopathological and electron microscopic study of the aortic wall of rabbits intoxicated with Solanum malacoxylon was performed. Histological examination showed local loss of the normal waviness of the elastic fibers and calcium deposits. Electron microscopic study of the corresponding areas showed a modified aspect of the smooth muscle cells with loss of some of their differential characteristics, especially their intracytoplasmic fibrils and densifications. The neighbouring elastic fibers showed an electron-dense peripheral band and sometimes a crystal deposit. X-ray microanalysis revealed the presence of a large amount of calcium in these crystals. Collagen fibers played no apparent role in this calcification. These findings support the idea that a local cellular alteration is necessary prior to elastic calcification. Two hypothetical mechanisms are proposed.