PURPOSE: To evaluate the MR imaging findings of ankylosing spondylitis involving the thoracolumbar spine. MATERIALS AND METHODS: We retrospectively analyzed MR imaging findings in ten patients with ankylosing spondylitisinvolving the thoracolumbar spine. All were male and ranged in age from 24 to 47 (mean, 33)years. MR images wereobtained using a 1.5T imager, and signal intensity changes of vertebral bodies were evaluated on sagittal T1- andT2-weighted images. Plain radiographic findings were also evaluated. RESULTS: On T1-weighted images, five casesshowed focal high-, two cases low-, two cases high- and low-, and one case iso-signal intensities at the cornersand/or along the anterior borders of the vertebral bodies. On T2-weighted images, seven cases showed focal high-and three, iso-signal intensities in those areas of the vertebral bodies. In one case which showed focal highsignal intensity on T1-weighted images and iso-signal intensity on T2-weighted images, multiple Schmorl's nodeswere seen in thoracolumbar spines. In all cases, signal intensity changes were more prominent in anterior portionsof the vertebral bodies. The shapes of abnormal signal intensities were vertical wedge, vertical band, and rounddot. Plain radiographs showed bamboo spine in three cases, squaring and focal sclerosis of vertebral bodies intwo, focal syndesmophyte in one, Schmorl's node in one, and no abnormal findings in three. CONCLUSION: Characteristic MR imaging findings of ankylosing spondylitis involving the thoracolumbar vertebral bodies werefocal signal intensity changes at the corners and along the anterior borders of the vertebral bodies.