The genetical forms of hypertrophic neuropathies, inherited either as recessive or autosomal dominant trait, are classified, according to Dyck (1975), as HMSN type I, III, and IV. Sporadic cases are also reported. We studied three patients, one with autosomal recessive inheritance, and two without family history, who had the following common features: --onset of symptoms before the age to two years; --slowly progressive course; --peroneal muscular atrophy with absent tendon reflexes; --reduction of MCV and SCV; --decreased number of myelinated fibers; --schwannian cell hyperplasia, with onion bulb complexes formation; --absence of aspects of hypomyelination; --increased number of collagen pockets and denervated Schwann-Remak cells or processes. On light microscopy, multilamellated onion bulbs of large size were found in a very high percentage in case 1, while there were either simple in type or in a lower percentage in case 2. In the third, case, onion bulbs were recognized only on electron microscopy. It is known that in the various kinships affected with type I of HMSN, the pathological changes of peripheral nerves differ greatly. Therefore, despite early onset of symptoms and varying degree of severity of nerve changes, all three cases have been classified within the group of HMSN type I. The different severity of nerve damage may suggest the possibility of a genetical heterogeneity in this disorder.