Subtalar arthrography was done in 37 feet of 35 patients in whom recurrent instability of the ankle was diagnosed. There were 16 male and 19 female patients, with a mean age of 29.1 years (range, 11-56 years). The mean interval between the injury and arthrography was 4 years 3 months (range, 6 months-22 years). Anteroposterior, lateral, and oblique radiographs were obtained for all patients. Any leakage during arthrography into the ankle, tendon sheaths, or sinus tarsi was recorded. An oblique view of the microrecess along the interosseous ligament and an anteroposterior view of the lateral recess just under the end of the fibula were examined. At surgery, 13 feet had combined injuries of the anterior talofibular and calcaneofibular ligaments, and 24 feet had isolated injury of the anterior talofibular ligament. The findings of the two groups were significantly different when examined for leakage into the ankle, leakage into the peroneal tendon sheath, and the presence of the lateral recess. Presence of contrast medium in at least two of these three positive arthrographic findings showed 92.3% sensitivity and 87.5% specificity in making the diagnosis of calcaneofibular ligament injury. Subtalar arthrography is valuable in making the diagnosis of calcaneofibular ligament injury in recurrent instability of the ankle.