The authors undertook a retrospective study to assess the role of magnetic resonance (MR) imaging in thoracic disk herniation. The initial MR images were interpreted independently of other findings. These interpretations were compared with the findings of plain and computed tomography (CT) myelography and surgery, when available. Sixteen thoracic disk herniations were confirmed with plain and CT myelography and/or surgery. Plain myelography was performed on 14 patients and showed focal ventral filling defects in nine. Results of CT myelography were equivalent to those of MR imaging with three pulse sequences (sagittal T1 and T2 weighted, axial T1 weighted) in the identification of all the abnormal levels. In two patients, the signal from the herniated disk was so low on all sequences that thoracic disk herniation had to be inferred from the mass effect on the spinal cord. Precise location of the abnormal level with body coil MR images was achieved in six of 13 patients.