This investigation used computed tomography (CT) to study the normal anatomy of the hindfoot and to demonstrate abnormalities in patients with rheumatoid arthritis, pes planovalgus , old trauma, and soft-tissue masses. The hindfeet of 10 normal volunteers and 17 patients were scanned in the coronal and axial transverse planes. The articular surfaces of the tibia, talus, and calcaneus were assessed, as were the relationships of each bone to the others. Normal subjects had markedly symmetrical hindfeet . The "heel valgus angle" (relating the calcaneus to the tibia) was 5.2 +/- 1.6 degrees (mean +/- standard error of the mean). The "sustentacular angle" (indicating the angle of elevation of the sustentaculum tali at the midsubtalar joint) was 18.3 +/- 1.3 degrees. The "medial offset" of the talar head with respect to the calcaneus (measured at the anterior subtalar joint) averaged 5.2 +/- 1.8 mm. Patients with rheumatoid arthritis had erosions involving both sides of the subtalar joint, leading to talocalcaneal alignment abnormalities. In patients with pes planovalgus the heel valgus angle was greater and the elevation of sustentaculum tali lower in the foot that was most severely affected. Bony talocalcaneal fusions, fractures, and the erosions of pigmented villonodular synovitis were detected on CT. The pattern of postoperative bone healing after attempted subtalar fusion could be demonstrated. We conclude that CT is a useful tool for pre- and postoperative evaluation of the hindfoot.