Report of a newborn infant with a caudal regression syndrome and a large myelocystocele. A small part of the transitional zone between the normal spinal cord and the myelocystocele displayed a triploid cord in cross sections, suggesting a kind of “triastematomyelia,” which was, however, finally considered rather to represent a special form of diastematomyelia than a true threefold split of the spinal cord. The probable pathogenetic background of the condition is discussed.