PURPOSE: To evaluate MR findings of postoperative diskitis following operation for intervertebral disk herniation. MATERIALS AND METHODS: Twelve cases with postoperative diskitis following operation for intervertebral disk herniation were included in this study. MR findings of postoperative diskitis were analysed to determine 1) the extent and pattern of alteration of the involved disks, 2) the pattern of destruction of endplates and vertebral bodies, and 3) the pattern of inflammatory extension into the surrounding soft tissue. RESULTS: 1) Disk alteration developed mainly at the middle and posterior portions of the disk, and was characterized by loss of intranuclear cleft at the involved portion of the disk and intranuclear abscess formation 2) Vertebral bodies involved ware symmetrically adjacent to involved disks and in three cases, bone abscesses within the endplates were detected. 3) The extension of inflammation yielded prevertebral or pre-/paravertebral masses (7 cases), epidural abscesses (5 cases), arachnoiditis (6 cases), and inflammatory masses (2 cases) beneath the posterior longitudinal ligament. CONCLUSION: Disk involvement was mainly at the middle and posterior portions of the disks, and there was accompanying intranuclear cleft loss. Symmetric involvement of the vertebral bodies adjacent to the involved disks was noted.