Measurement of the cortical thickness of the tubular bone has recently been know as a one of the best method diagnosing osteoporosis. It is suggested that the combined cortical thickness of better than more complicated indices. The authors have attempted to measure the combined cortical thickness of the lower shaft of humerus and mid-shaft of the metacarpal, and review of literatures were carried out. The results are as follows : 1. The mean value of combined cortical thickness (CCT) of metacarpus and humerus of various age groups has been measured and calculated on roentgenograms in 791 patients. In the male, CCT of 2nd metacarpus is 4.7$pm$0.15mm, 3rd metacarpus is 4.3 $pm$0.11mm, 4th metacarpus is 4.1$pm$0.20mm. on 30-39 age group, and CCT of humerus is 9.4$pm$0.28mm. In the female, CCT of 2nd metacarpus is 4.6$pm$0.17mm, 3rd metacarpus is 4.3$pm$0.12, 4th metacarpus is 4.2$pm$0.41mm. on 40-49 age gropu, CCT of humerus is 8.6$pm$ 0.13mm. on 30-39 age gropu (Table 2,3) 2. Measurement of combined cortical thikness in the humerus demonstrated a gradual decrease of the cortext after 40-49 age groups in both sexs, while in the case of metacarpus, measurement of CCT in the 2nd metacarpus only demonstrated a gradual decreases of cortex with age in female. (Fig. 2) 3. Reduction rate of CCT is $1.5pm$$pm$0.31mm/10 yrs between 50-59 age group and 60-69 age group in the humerus, in male. Mean reduction rate of CCT is 0.6$pm$0.21mm/10 yrs after 30-39 age group in the female.