The correlation between the white and red fibers of the skeletal muscle and the large and small alpha ventral horn cells in peripheral neuromuscular system was studied in cats. In order to damage selectively the small nerve fibers 0.0066% sublimate solution was injected into the cat peripheral nerve (after HIRATA). By this procedure, the degeneration of the small ventral horn cells and of the red muscle fibers was selectively caused, while the large ventral horn cells and white muscle fibers were slightly affected. To damage the large nerve fibers, 80% alcohol was used (after HIRATA). In this case, the large ventral horn cells and the white muscle fibers were selectively degenerated. From the results, the following correlation may be reasonably inferred: large ventral horn cell→large peripheral nerve fiber→white muscle fiber small ventral horn cell→small peripheral nerve fiber→red muscle fiber The peripheral nerve was lesioned at its entering point into the supplying muscle and their regeneration was strained, 10-25 days after the animals were sacrificed, then the spinal cord was examined with NISSL staining and the muscle with Sudan-Black-B. Each number of the degenerated large and small ventral horn cells and that of the red and white muscle fibers were counted. The muscles used were the M. biceps brachii, M. palmaris longus, M. gracilis and median head of M. gastrocunemius, and the innervation ratio of these muscles were 1:195.9, 1:102.7, 1:154.6 and 1:209.3 respectively. The ratio of the number of the large ventral horn cells to that of the white muscle fibers (the innervation ratio to the white muscle fiber) was smaller than that of the small ventral horn cells to the red muscle fibers (the innervation ratio to the red muscle fiber) except for the M. gracilis. The ratio of the number of the degenerated large ventral horn cells to that of the small ventral horn cells was 1.66:1 in M. biceps brachii, 1.88:1 in M. palmaris longus, 1.58:1 in M. gracilis, 1.79:1 in the median head of M. gastrocunemius. The ratio of the number of the white muscle fibers to that of the red muscle fibers was 1.41:1 in M. biceps biachii, 1.51:1 in M. palmaris longus, 1.94:1 in M. gracilis and 1.53:1 in median head of M. gastrocunemius, respectively. It may depend upon that these muscles participate not only phasic movement but also stronger tonic contraction than other muscles. The arrangements of the cells groups in the ventral horn were as follows: M. biceps brachii is mainly supplied by the dorsolateral group, M. palmaris longus by the retrodorsolateral group, M. gracilis by the ventrolateral group, the median head of M. gastrocunemius by the central group, respectively.