Histological changes of neuropathy induced by chronic administration of acrylamide in the rat were investigated quantitatively under the light and electron microscope. The effect of the mixture of thiamine disulfide, pyridoxine hydrochloride and aquocobalamin on the neuropathy was also investigated. Following parameters were used : (1) distribution of transversal area of medullated-nerve fibers, (2) degree of transformation of medullated-nerve fibers, (3) ratio of transversal area of myelin to that of medullated-nerve fibers, (4) stromal area of sciatic nerve, (5) numbers of degenerated medullated-nerve fibers and Schwann's nuclei in the unit area, (6) RNA level in anterior horn cells of the spinal cord of the lumbar area and (7) histochemistry of motor end-plate. A beneficial effect of the mixture of vitamin B group was observed on the acrylamide-induced changes of the transversal area of medullated-nerve fibers and the number of Schwann's cells.