PURPOSE: To evaluate whether progression of compression correlates with bone densiometry index in patients who were treated conservatively for osteoporotic compression fracture of thoracolumbar spine. MATERIALS AND METHODS: Using the results of bone densiometry, 30 patients who were treated conservatively for osteoporotic compression fracture of thoracolumbar spine between March 2002 to March 2005 were categorized into 4 groups; above 80%, 70 to 80%, 60 to 70%, and below 60%. We compared the measurements of sagittal index and anterior vertebral height from the plain radiographs taken at the time of injury and following three consecutive months after the injury. RESULTS: Patients with lower bone densiometry index had greater amount of compression at the time of injury and more rapid progression of compression. We also found that progression of compression was lowest during the first month after injury in all groups. CONCLUSION: Patients with low bone densiometry index in osteoporotic thoracolumbar compression fracture are susceptible to more rapid progression of compression and should have early brace application and longer duration of treatment for osteoporosis.