Twenty-three patients with sacral agenesis evaluated at Newington Children's Hospital between 1959 and 1977 were classified according to patterns of morphologic deficiency in the bones and articulations. Motor deficit in these patients corresponded, within one level, to vertebral loss; sensory deficit did not correspond. The major orthopaedic problems often associated with sacral agenesis are spinopelvic instability, scoliosis, myelomeningocele, hip dislocation and contracture, knee contracture, and foot deformity. These can be controlled or corrected by proper orthopaedic management.