1. Four cases of true congenital vertical talus are described; in three of the four cases there were other major deformities of the skeleton. All were treated by open operation; the operation sacrificed part of the substance of the navicular bone, which was placed between the forepart of the calcaneus and the head of the talus.
2. The results five to ten years after operation show that stable reduction was maintained without any further treatment. They suggest, however, that more of the navicular bone could have been removed or that the whole navicular might be excised, at least in the more severe deformities.
3. Congenital vertical talus resembles club foot (equino-cavo-varus) in that difficulty in reduction and in maintenance of the reduction results from the tension in the medial pillar of the foot. Easing of the tension can result in recurrence of the dislocation or, alternatively, a reversal of the deformity.