SUMMARYThe clinical manifestations in infantile neuroaxonal dystrophy are sufficiently characteristic to allow a presumptive diagnosis. They consist of slowly progressive weakness, muscle atrophy, and hypotonia beginning in late infancy, associated with signs of corticospinal tract involvement, urinary retention, visual and other sensory deficits, occurrence in familial pattern, and absence of convulsive seizures. In 7 patients with these clinical manifestations, we found peripheral nerve lesions not previously described. Clinical signs were used to select the proper biopsy site. It may be possible to confirm a clinical impression of INAD by finding characteristic axonal changes in peripheral nerves, using ordinary biopsy technique and standard methods of light microscopy. Electron micrographs of peripheral nerve tissue from one patient revealed abnormalities of axons, myelin sheaths, and Schwann cells.