Monozygotic male twins died at the age of 6 1/2 and 7 1/2 years respectively after a progressive course of mental deterioration, hypotonia, spasticity, optic atrophy and seizures that had commenced at the age of 2 years. Both patients showed generalized neuroaxonal dystrophy (NAD), marked by numerous spheroids, iron-positive pigment and lipophanerosis of the pallidum. NAD can be classified as a generalized form without pigmentation of the pallidum (infantile type of Seitelberger), a juvenile type of Rozdilsky, a generalized form with pigmentation (cases described here), and localized forms (infantile, late infantile, juvenile = classic Hallervorden-Spatz disease, adult types).