The subject of occult spinal dysraphism or myelodysplasia is reviewed from standpoints of embryology, clinical manifestations, and treatment, and the management of 73 cases summarized. In general, these concealed lesions arise from developmental variants in the most distal part of the neural tube, a situation which may cause distortion or partial absence of neural tissues and also lead to damage from compression or traction. Lipomyelomeningocele and congenital dermal sinus are two examples of the many types of such lesions, but some are more complicated, and borderline myelomeningocele-like forms occur. Incontinence, deformity or weakness of the feet, impaired gait, and other difficulties may appear late and increase with growth. Surgical treatment is advised to reduce chances of delayed or progressive loss of function.