In five members belonging to a Swiss kinship the typical signs of Roussy-Levy's syndrome are described, such as disturbances of gait and of standing, areflexia, foot deformities, slight muscular weakness and atrophies, minimal sensory disturbances and the typical course of the disease. The patients have been examined electrophysiologically and disturbances of sensory conduction velocity and sensory nerve action potentials are described. The question whether Roussy-Lévy's syndrome represents a disease entity or not, is discussed. The authors feel that the syndrome belongs to HMSN type I.