The tunica albuginea (TA) of the penis is thought to play a major role in the erection mechanism. It functions by compressing the subalbugineae venulae, which promotes the slower venous flow during erection, and provides a fibrous frame to give an inextensible support for the vessels and nerves. It acts as the inextensible enclosing structure which contains the erectile tissue and gives the erect penis its shape. The functions of the TA result from its structure, consisting for the most part of collagenic and elastic fibers. This study investigated, with the aid of scanning electron microscopy (SEM), the microarchitecture of the TA and the spatial relation of its fibers in ten impotent patients and in six control subjects with normal erectile function. The arrangement of elastic fibers in the TA seems to account for their function, which is to prevent the overstretching of collagenic fibers during maximum intracavernous pressure. In impotent patients, a reduction in the elastic fibers in the TA appears to produce disorders in the arrangement of the collagenic fibers. These alterations in the architecture of the TA in impotent patients can give rise top erection disorders.