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We reviewed 104 consecutive cases of closed dysraphism in patients seen at one institution between December 1984 and June 1987. All patients had myelographic studies, and 43 had associated CT examinations. Clinical and surgical findings (64 patients) were correlated with myelographic information. Twenty-three patients (22%) with clinical or plain film findings compatible with dysraphism had normal-appearing cords on conventional myelography, movement between supine and prone positions, and no lesions in the spinal canal. Cerebellar tonsillar ectopia (majority of tonsils between foramen magnum and C1) was found in 17 patients (16%). Six patients (6%) exhibited varying degrees of hydromyelia. In the supine position, CT-myelography of meningoceles, meningomyeloceles, or lipomeningomyeloceles may limit demonstration of the neural placode and nerve roots because of compression of the CSF-containing sac. In the decubitus position, CT scans improved demonstration of neural tissue-CSF space relationships. CT scans were useful in demonstrating anomalous paraspinal bones, diastematomyelia spurs, and spinal and sacral bone deficiency. Axial CT-myelography of intradural lipomas showed apparent neural tissue extension into the lipomas.