Three-dimensional (3D) MR Myelography is a new technique using constructive interference steady-state (CISS) sequences, which are characterized by a symmetric flow compensation enhancing CSF signal intensity compared with neural and extradural structures. 3D myelographic projections with different rotation angles are obtained from the 3D dataset with a mathematical algorithm called maximum intensity projection (MIP). Myelographic projections yield a global view of subarachnoid spaces and of root sleeves with no intrathecal contrast agent injection. This study was aimed at assessing the feasibility, the clinical value and the diagnostic accuracy of 3D MR Myelography in comparison with conventional myelography. From September 1992 to January 1994, thirty-five myelograms were performed. The study population consisted of 10 volunteers, 8 patients with traumatic brachial plexus lesions, 7 with herniated disks (4 lumbar and 3 cervical disks), 4 with sacral radicular cysts, 2 with spinal vascular malformations, 3 with extramedullary intradural neoplasms (2 cervical neuromas and 1 cervical meningioma) and 1 with an intramedullary tumor (a conus medullaris ependymoma). All patients underwent SE MRI and conventional myelography (22 lumbar injections, 3 cervical injections of nonionic iodinated contrast agent) followed by CT (CT myelography). This trial demonstrates the feasibility of 3D MR myelography in the study of the cervical and lumbar spine: its results are comparable to those obtained with conventional myelography also in some specific indications like traumatic brachial plexus injuries, where invasive conventional myelography is usually thought to be essential.