A radiologicla study on sesamoid bones of hands and feet was done in Korean adults who visited the Capital Armed Forces General Hospital of Korea during last 10 months from Jan. 1, to Oct .30, 1979. The incidence of presence or absence of sesamoid bones in each possible site and shape and partition were studied in 250 males and 200 felames. The results are as follow : 1. In hands. two sesamoids are present at metacarpophalangeal joint of thumb in all and one at metacarpophalangeal joint of little finger in half, metacarpophalangeal joint of index, interphalangeal joint of thumb, metacarphphalangeal joint of middle finger and metacarpophalangeal joint of ring finger were other sites, in order to frequency. 2. In feet, two sesamoids are present at metatarsophalangeal joint of great toe in all, but the incidence at other sites are much lower comparison to hands and the sites are interphalangeal joint of great toe, metatarsophalangeal joint of 5th toe, metatarsophalangeal joint o 2nd toe, and metatarsophalangeal joint of 4th toe in orderfrequency. 3. In comparison with sexes, the incidence is a little greater in female at every site. 4. In general, the partition line of sesamoid bone is transverse, and fracuture line of sesamoid is longitudinal. 5. In comparison with Europians, the incidence of sesamoid bone at interphalangeal joint of thumb and great toe is about half, and at other sites, except metacarso phalangeal joint of thumb abd great toe, the incidence was smaller in each site.