Sacrum is a triangular bone formed by fusion of five sacral vertebrae. It is wedged between two hip bones. Its base articulates with 5th lumbar vertebra and apex with coccyx. Complete agenesis of the dorsal wall of sacrum was observed during one routine osteology tutorial. The same is presented. The sacral canal was completely open posteriorly due to non fusion of the laminae from S1 to S5. The sacral canal is formed by sacral vertebral foramina. The anterior wall of the canal is formed by fusion of the sacral vertebral bodies. The fused laminae, spines and ossified ligamenta flava form the dorsal wall. The sacral canal is triangular in cross section and contains cauda equina, filum terminale and spinal meninges. Duramater and arachnoid mater end at middle of sacrum (generally at the level of S2) while filum terminale is continuation of piamater till coccyx. Knowledge of variations in the dorsal wall of sacrum due to congenital factors is essential for anesthesiologists, surgeons and physicians to treat the related disorders. Study of the variation in anatomical features of sacral hiatus and dorsal wall of sacral canal is important with regards to its clinical application in caudal epidural anesthesia. Sacral approach to epidural space is reliable and effective means of blocking sacral nerves.