During a 3-year period, 14 of 319 patients (4.4%) with surgically proved primary hyperparathyroidism had spinal rarefaction with vertebral crush fractures but no unequivocal roentgenographic evidence of osteitis fibrosa generalisata. All complained of back pain, and this was the presenting complaint in 9 of the 14 patients. This incidence was significantly higher (P less than 0.001 for women; P less than than 0.01 for men) than the incidence of similar roentgenographic findings among patients of the same age undergoing operation for protruded intervertebral disks during this same time period. Although tradition equates roentgenographically evident bone disease in primary hyperparathyroidism with the classis findings of osteitis fibrosa generalisata, our observations emphasize that patients with primary hyperparathyroidism occasionally may present in a manner that is indistinguishable symptomatically and roentgenographically from that of postmenopausal or senile osteoporosis.