For the measurement of the bone quantity, various methods have been used. Recently, the methods such as a microdensiometry, single photon absorptiometry, quantitative computed tomography were introduced. However, these methods are expensive modalities to be used in daily clinical practice. For the evaluation of the osteoporosis, author's observed Saville's grades, spine contral score and spine fracture on the simple spine roentgenograms of 346 patients over 40 years of age who were exsmined due to their backache at the Department of Orthopedadic Surgery, Kang Nam St. Mary's Hospital, Seoul, and following results were obtained: 1. The percentile incidence of osteoporosis with regard to age and sex : (1) The percentile incidence of osteoporosis over Saville's Grade I was 59.2%(205 of 346 persons); in males 47.4%(55 of 116 persons) and in females 65.2%(150 of 230 persons). (2) The percentile incidence of osteoporosis over Grade 1 in 5th decade was 27.2%(17.1% in males and 33.9% in females), 55.8% in 6th decade(46.6% in males, and 60.4% in females), 78.1% in 7th decade(64.7% in males, and 82.9% in females), 93.7% in 8th decade(87.5% in males and 97% in females), and 100% in both sexes of 9th decade. (3) The percentile incidence of Grade 1 osteoporosis in 5th decade was 23.9%, and in 6th decade it was 46.7%. Thus, Grade I osteoporosis was most common in these age groups. In 7th and 8th decades, Grade I osteoporosis was more common in males, while in the females ot these age groups Grade II was more common. There was no sex difference in the incidence of osteoporosis after the age of 80. Grade IV osteoporosis was found only in a woman who had hysterectomy 7 years ago, and has suffered from Parkinsonism for 3 years. (4) The overall incidence of Grade I osteoporosis was 34.6%, and Grade II was 21.3 %. The incidence of osteoporosis over Grade III was 1.7% in males, and 6.5% in females. 2. Incidence of osteoporosis assessed by Barnett's central score and its correlation with Saville's assessment: (1) The central score obtained at the 3rd lumbar spine ranged from 71.4 to 106.4. The number of cases were 16 in the score range of 70 to 80, 93 in the score range of 101 to 110, and 5 in the score range of 111 to 120. In consequence the most high incidence was in the score range of 91 to 100. (2) Grade O Oxteoporosis corresponded with the central score of 96.4 on an average (range : 86.8 to 106.4), Grade I corresponded with 91.6 (range : 85.7–103.1), Grade II corrosponded with 86.4 (range : 78.3–96.9), Grade III corresponded with 79.4 (range : 71.4–91), and Grade IV corresponeded with 75.8. (3) Barnett defined the spine is osteoporotic, when the central score is below 80. However, in this study only 16 patients(4.6%) had the score below 80. No bodies having Grade 0 and I osteoporosis had the score below 80; of those 16 patients having the score below 81, 5 were Grade II, 10 Grade III, and one Grade IV. Through this study, it is clesr that there is no correlation in these two assessing methods. The central score below 80 was found in severely porotic patients such as Grade III and IV, but was not found in most cases of Grade I and II osteoporotic patients. (4) The vertebral defromity was found only in 38 cases (10.9%), and it was found only in 18.9% of osteoporosis patients. The percentile incidence of deformity was 5.3% of Grade I, 31% of Grade II and 52.9% of Grade Ill. (5) Of these deformities, wedge-shaped one was found in 6 cases of Grade I porosis, 20 of Grade II, and 3 of Grade III. Cod-fish vertebrae (biconcave) were found in 2 of Grade II and 4 of Grade III. The flattened body was found in 1 of Grade II and 2 of Grade III. Thus, biconcave and flattened vertebrae were found only in the porotics over Grade II severity. (6) In 24 cases, one body was deformed, and in 14 cases multilevel vertebral deformities were found. In these 20 cases had deformity in the Ll, 10 cases each in T12 and L2, 7 cases in L3, 6 cases in L4, and 4 cases in Tll. In summary, the most deformities were in the dorsolumbar region. (7) Fracture was induced by trauma in the 11 cases(29%), among which 10 were wedgeshaped, and the rest was flattened. The biconcave vertebra was found not to be related with injury.