A CASE OF an isolated intraspinal lumbosacral neurenteric cyst in a 5-year-old girl with partial sacral agenesis is reported. The cyst wall contained transitional epithelium and smooth muscle characteristic of the urinary bladder, suggesting a possible cloacal origin of the cyst. No prior cases of concomitant neurenteric cysts with partial or complete sacral agenesis have been reported, and the occurrence of an isolated intradural extramedullary sacral neurenteric cyst is rare. The possible pathogenesis of this lesion is described.