Meningocoele manqué is a congenital anomaly relating to the spinal cord, cauda equina and the filum terminale commonly found on exploration of the spinal cord in cases of spina bifida occulta. The anomalies consist of fibrous bands, aberrant nerve roots and adhesions within the theca which may tether or press on the neural structures so interfering with nerve conduction and causing increasing neurological deficit. Treatment is to free the neural structures from these bands and adhesions surgically. An account is given of 45 cases with a discussion of their similarity to cases of meningocoele, thus justifying the naming of a previously undescribed clinical entity. Meningocoele manqué demonstrates the relation of spina bifida occulta to spina bifida cystica as having a similar origin differing only in degree of severity. All the cases discussed are drawn from a personal series of 200 cases of spina bifida occulta which have had surgical exploration of the spinal cord.