Anatomically, we have known that the first toe is composed of 2 phalangeal bones (proximal and distal phalanx) and the second, third, fourth, fifth toe are composed of 3 phalangeal bones (proximal, middle, and distal phalanx). But in Korean the 5th toe is commonly seen as 2 phalangeal bones in foot plain X-ray. In this study, we observed the numbers of phalangeal bones of fifth toe in Korean and analyzed the relation with several environmental factors and genetic factor. The data of occupation, age, body weight and foot length as well as the foot radiograph were obtained in 175 persons without any foot lesion. With the coorperative persons among them showing triphalangeal 5th toe as the index cases, radiograph of 12 family were studied to analyse the pedigree. As result, total frequency of the 5th toe symphalangism was 74.29% (male 74.2%, female 73.36%). There was no statistical difference between male and female. The bilaterality of the symphalangism was 98.46%. The occupation group were farmer, labor, self-support, white collar, student, housewife, there was no correlation between the kind of occupation and the frequency of the symphalangism. Also there was no correlation between body weight or foot length and the symphalangism. In conlusion, the two-phalanged fifth toe might be related with genetic factor rather than several environmental factors such as sex, age, occupation, body weight and length of foot. From the pedigree study we concluded the genetic trait of the triphalangism might be the autosomal recessive.