Thirty eight extraocular muscle biopsies obtained from thirty patients (1 normal and 29 affected with various kinds of ocular motility disorders such as strabismus, Duane’s syndrome, paralysis), were studied by electron microscopy. Except for the control biopsy considered as normal, they showed: atrophy, disorganization of myofilaments, double Z-disks, rods, curving arrays of myofibrils, concentrically disposed electron-dense sarco- tubules, clusters of mitochondria with numerous modifications of their cristae, and subsarcolemmal inclusions, such as dense bodies, laminated bodies, lipofuscin granules and lipid droplets. In addition, subsarcolemmal granulo- fibrillar aggregates, characterized by periodic granulated foci spaced at about 120 nm intervals, were seen in all the biopsies, even in that of the control case. The authors stress the pecularity of the granulo-fibrillar aggregates which, up to now, have never been described in skeletal muscles and the function of which in the extraocular muscles fibers is impossible to define. They point out the difficulty in determining if the motility disturbances may be related to the various changes observed in extraocular muscles of squinting eyes.