The abnormal bony feature found most consistently in clubfeet is talar distortion. The significance of the talar distortion for mobility of the tibiotalar joint was investigated. Twenty-seven congenital clubfeet in 19 patients were examined at a minimal followup of 20 years. In all patients Turco's posteromedial release was done because of idiopathic clubfoot. Radiographic assessment of the feet included measurement of the talocalcaneal angle and index, and the tibiocalcaneal angle. The degree of talar flattening was estimated by the ratio of the curvature of the talar dome to the length of the talar bone (radius to length ratio). Three-dimensional gait analysis was done to assess the dynamic range of ankle motion. The static range of motion was measured with a goniometer. The degree of talar flattening correlated significantly with the dynamic range of ankle motion but not with the static mobility. For assessment of idiopathic clubfoot, evaluation of talar flattening should be done because of its significance for dynamic ankle mobility.