The difference of patterns of costal cartilage calcification in male and female had been first described by Fischer in 1955. Thereafter several reports were published, but specific clinical significance was not found. During the period from January, 1978 to December, 1978, we, in the Department of Radiology, Jeonbug National University, studied 2164 cases that showed the entire 12 pairs of ribs. Among these we detected 1494 cases of costal cartilage calcification and analyzed the relationship to age and sex, patterns of costal cartilage calcification, and frequent sites of calcification. Patterns of costal cartilage calcification were classified into six groups - type I : central, type II : marginal, type III : junctional type, type IV : railroad, type V : diffuse, type Ⅵ : mixed. Results are as follows ; 1. In a total of 2164 cases, calcification of costal cartilage was present in 1494 cases (69.0%). Of 1181 males 780 cases (66.0%) showed calcification, and of 983 females 7 4 cases (72.6%) showed calcification. 2. In 439 cases of males, except for 341 cases that showed calcification within the first costal cartilage, patterns of costal cartilage calcification were as follows; marginal type in 265 cases (60.4%), junctional type in 134 cases (30.5%), mixed type in 21 cases (0.5%), central type in 17 cases (3.8%), and railroad type in 2 cases (0.5%). Diffuse type was not present. 3. In 492 cases of females, except for 222 cases that showed calcification within the first costal cartilage, patterns of costal cartilage calcification were as follows; central type in 336 cases (68.3%), junctional type in 94 cases (19.1%), mixed type in 24 cases (4.9%), railroad type in 19 cases (3.9%), and diffuse type in 14 cases (2.8%). 4. When central calcification was observed, predictive value to female was 94.7%. When marginal calcification was observed, predictive value to male was 98.4%. 5. Males frequently showed calcification in upper costal cartilages, and females in lower costal cartilage.