This article discusses the features of the pathogenesis and symptoms of two of the most common causes of polyneuropathy. On the one hand, the alcoholic genesis of nerve fiber damage is discussed - we will consider how chronic alcoholism provokes the appearance of polyneuropathy. On the other hand, an equally important and frequent inducer of a decrease in all types of sensitivity in patients is diabetes mellitus. Moreover, in some cases, polyneuropathy can occur even before the establishment of diabetes mellitus as a causal diagnosis. Thus, we see the need to highlight important aspects of pathogenesis, and, despite the differences in the development of both processes, the commonality of symptoms.