A brief review of the literature on the subject is followed by a report on the technique, biomechanics and indications for subtalar arthroereisis by means of « calcaneal cndoorthosis ». The technique is directly derived from the arthroereisis described bv Rccarcdo-Alvarez and Burutaran (« calcaneal stop ») used in the sumical correction of calcaneal valgus. The operation limits subtalar excursion in the desirsd direction without eliminating the plane between the astragalus and the calcancum or damaging the anatomical integrity of the subtalar joint surfaces and the tarsal tissues, The operation is also easily repeated in the event of failure. A modified spongv bone screw is implanted in an oblique dorsoplantar proximodistal direction so that the head of the screw is in contract with the lateral astragalar process. Under weight, the screw exerts a two-fold corrective action: it limits the pronation of the calcancum and rotates the astragalus to correct the angle of astragalocalcancal divergence. The operation can be used to treat calcaneal valgus and has been combined with other surgical techniques in the treatment of astragalar protrusion and flat foot with secondary valgus deformity.