Six hips in four patients with hip pain, limited range of motion, no antecedent trauma, and normal laboratory studies demonstrated roentgenographic evidence of periarticular osteoporosis. The subchondral cortex was attenuated. There was little or no cartilage loss. The preliminary diagnosis was transient osteoporosis (migratory osteolysis, regional osteoporosis). This problem is most frequently seen in the hip joint in two population groups: men near 40 and women in the third trimester of pregnancy. Other joints may be involved and the process may regress in one joint but recur in another. Diagnosis is based on typical clinical and roentgenographic observations including an aspiration of sterile joint fluid. Radioisotope scanning may be helpful. Bone or synovial biopsy sampling is not necessary. Proper management requires accurate diagnosis and conservative treatment of a cooperative patient. Pain may persist for six months or longer. Treatment consists of analgesics, protection against stress fractures, and physical therapy for prevention of contractures.