Background: Radiographic assessment is still used to evaluate flexible flatfoot in children. Methods: To find a set of radiologic parameters for assessing this disease, we studied 53 children aged 10 to 14 years. The degree of plantar collapse was measured by Viladot’s classification (grades 0–4). The degree of valgus deformity measured in the heel in a standing position, the presence of painful points, and functional limitation during daily-living activities were also reported. The children underwent standard radiography of the foot under load. On the dorsoplantar view, the talocalcaneal, hallux metatarsophalangeal, and first intermetatarsal angles were measured. On the lateral view, the talocalcaneal, Costa Bertani, talometatarsal, talonavicular, and tibiotalar angles were measured. The radiographic measurements were compared with the data reported in the literature and were correlated with the clinical parameters studied (degree of flatfoot, valgus deviation of the heel, pain, and functional limitation). Results: The radiographic measures that resulted increased with respect to the reference values reported in the literature for the Costa Bertani (93.1% of feet), talometatarsal (93.5%), talonavicular (89.1%), and tibiotalar (69.7%) angles, all in the lateral view. Of the angles assessed in the dorsoplantar view, the hallux metatarsophalangeal (11.1%) and first intermetatarsal (24.2%) angles were increased. The degree of flatfoot was correlated with the Costa Bertani angle ( P < .0005). In the group with pain, the lateral talocalcaneal ( P = .016) and first intermetatarsal ( P = .02) angles were increased compared within the group without pain. Conclusions: Despite technical limitations, we still consider standard radiography of the foot, combined with clinical examination, to be a valid tool for assessing flexible flatfoot in children, especially when surgical treatment is expected and when a basic measure of the structural setup of the foot is necessary. (J Am Podiatr Med Assoc 100(6): 463–471, 2010)