Radiologic findings of faltfoot are flattening of longitudinal arch of foot and arthritis of tarsal bone joins. No definte diagnostic critieria is still demonstrated between normal and flatfoot in longitudinal arch flatten-ing in Korean. Authors suggest criterias for longitudinal arch curve by measuring of the angle between first metatarsal bone axis and ground baseline (metatarsal angle) the height of navivcular bone from ground baseline(navicular height). 50 cases of normal group and 14 cases of flatfoot are reviewed. Results were as follows : 1. In normal group matatarsal angle is 30 $pm$2.5。 navicular height(II) is 29.3$pm$3.4mm 2. In flatfoot group metatarsal angle is 20.8$pm$3.5。 navicular height(II) is 16.3$pm$3.7mm. 3. In diagnosis of flatfoot measurement of metatarsal angle and navicular height are clinically significant.