Following the definition of the leukodystrophies as degenerative demyelinating proeesses caused by metabolic disorders a pathogenetical classification of the leukodystrophies is given. Metabolic processes in the narrower sense (enzymopathies) and dysgenetic processes are distinguished. In the special part according to this classification the neuropathological characters of the representative leukodystrophies are described. Different types of loss of myelin sheaths, structural features of stored products, localisation patterns etc. are demonstrared. Etiogenetic, nosological and diagnostic aspects are discussed. Probable conditions of the inflammatory demyelination syndrome of adrenoleukodystrophy are considered. The possible coincidence of dysmyelination and demyelination in early manifested leukodystrophies in the frame of the Pelizaeus-Merzbacher-syndrome is emphasized. The findings in a connatal case of Pelizaeus-Merzbacher-syndrome are described.