Early detection of skeletal disorders was very important role in establishing therapeutic modality and prevention of complications. Since Tc-99m-phosphates derivatives used in bone scan agent, remarkable improvement was noted in effectiveness, cost, radiation hazard to patient and image quality than previously used agents such as strontium or fluoride. Bone scan with Tc-99m-MDP was done in 155 cases for early diagnosis of skeletal disorders at Severance Hospital, College of Medicine, Yonsei University from August, 1980 to May, 1982 were analyzed both clinically and radiologically, and the following results were obtained. l. Among 19 cases of avascular necrosis, positive cases were 17 (89.5%) in bone scan and 6(31.6%) in X-ray. Positive pattern could be classified into 3 types and the radionuclide uptake in the femoral head was decreased in 3 cases which was negative in X-ray and duration of their symptoms was within 4 months. 2. Fifteen among 17 hip fractures or dislocations were positive in bone scan. In 12 (80.0%) among 15 cases, complications were revealed and positive cases in X-ray were 7(58.3%), which were all positive in bone scan. 3. In 20 bone scans for early diagnosis of acute osteomyelitis, positive in bone scan were 17 and 14 (82.4%) of 17 cases were finally diagnosed as acute osteomyelitis. Among 15 cases diagnosed as acute osteomyelitis, positive in X-ray were 8(53.3%) and sensitivity of acute osteomyelitis in bone scan was 93.3%. 4. In 25 cases of the suspected infection of the joint, 15 were positive in bone scan and among them, cases diagnosed as pyogenic arthritis were 12 (80.0%) and positive in X-ray were 2 (16.7%). Only one of 10 cases of transient synovitis of the hip joint was positive in bone scan. 5. In rheumatoid arthritis, 13 of 15 cases were positive in bone scan and 10 among them were revealed the diffuse uptake of the radionuclide in the joint. In degenerative arthritis, 7 of 8 cases were positive in bone scan and they were revealed the focal uptake of the radionuclide in the same site where the bone was changed in x-ray. 6. Among 28 cases showed spine fracture in X-ray after trauma, 15 (53.6%) were positive in bone scan. In spine fracture, it was difficult to differentiate fresh fracture from old fracture with bone scan. The positive duration of bone scen in fracture of weight bearing bone was longer than in spine fracture. Rib fracture which was not found in X-ray could be diagnosed with bone scan.