To elucidate the role of the human central canal on the physiology and pathogenesis of acquired syringomyelia, we analyzed the age-related morphologic changes in the normal human central canal of the spinal cord. The subjects included 158 autopsy cases ranging in age from 1 week postnatally to 116 years of age. Each segment of the whole spinal cords was investigated from the C3 to S3 levels. The microscopic pictures of the central canal were classified as patent or occluded at each level for each age decade. The patency rate under 1 year of age was 100% in almost all the segments, which markedly decreased in the second decade, and the canals were occluded in all the segments with advancing age. According to the longitudinal pattern of the central canal occlusion, 19 of 20 cases where the canals were patent in all segment levels were less than 10 years of age. Cases in which the canals were occluded in all segment levels appeared in the second decade, and their number increased gradually with advancing age. The occlusion of the central canal started at the T6 and L5 to S2 levels. We suggest that the central canal does not function after infancy because of its occlusion, and that it is not involved in the development of syringomyelia in adult patients.