Traumatic sacral fractures are most often due to motor vehicle or industrial accidents and are commonly associated with pelvic, urogenital, and neurological injuries. In recent years, a more subtle type of sacral fracture, not associated with major trauma, has been described. It is an osteoporotic insufficiency fracture that presents as low back pain in elderly patients, especially postmenopausal Caucasian women. It may escape detection unless radionuclide bone scans, tomograms, or computed tomograms are obtained. The radiographic features have been detailed in various publications, but little has been reported about the clinical features, treatment, or ultimate outcome of patients with osteoporotic sacral fractures. We have reviewed the charts and radiological studies of 13 women and 3 men who sustained this type of fracture between 1983 and 1986. All of these patients were Caucasian. The average age was 71 years. The most common presenting symptom complex was diffuse low back pain accompanied by hip, buttock, or thigh pain. Pertinent physical findings were limited to tenderness on palpation of the sacrum and a decreased range of low back motion. The osteoporotic fractures were seldom noted on plain roentgenograms of the sacrum, but were readily defined by sacral tomography or computed tomography. Radionuclide bone scanning also proved helpful in making the diagnosis by localizing the process. Treatment was medical and consisted of therapies designed to reduce pain and to combat the associated osteopenia. Of our 16 patients, 11 had complete pain relief, 2 had substantial pain relief, 2 noted decreasing pain before they died of other causes, and 1 was followed less than 1 month. The average time from diagnosis to resolution of the symptoms was 6.5 months. We conclude from our review that, when an elderly or osteoporotic Caucasian patient develops pain in the lower back, hip, or buttock, the physician needs to consider an osteoporotic sacral fracture in the differential diagnosis. The presence of such a fracture can then be identified and diagnosed with the appropriate radiographic studies (primarily radionuclide bone scanning followed, if positive, by computed tomography). As with other spinal osteoporotic fractures, the outlook for eventual pain relief is good.