Serum lipids were determined in 40 cases of polyneuropathy including 17 cases of Charcot-Marie-Tooth peroneal muscular atrophy, 7 cases of Dejerine-Sot-tas polyneuropathy, 7 cases of Guillain-Barré syndrome, 2 cases of diabetic polyneuropathy, 2 cases of toxic polyneuropathy and 5 cases of polyneuropathy of unclear aetiology. In the studied material shifts were observed in the composition of serum lipids, in particular, sphingomyelin and cholesterol esters. No correlation was found beteen the type of lipid pattern changes and the clinical syndrome, type of histological changes in the sural nerve, the age at onset, as well as the duration of the disease. The probable mechanism of development of changes is discussed.