Seventy-three patients suffering from lateral instability of the ankle joint, bilateral in 6 cases and combined with subtalar instability in 25, were operated on using the distal part of the peroneus brevis tendon. The tendon was pulled through two bore canals in the lateral malleolus and fixed in a bore hole in the calcaneus. The direction of the tendon in relation to the calcaneus and the talus was varied depending upon the type of instability. At 9 and 24 months follow-up, all but 2 patients had substantial reduction of the radiographically measured instability. No subtalar instability could be disclosed, and all the patients could return to normal levels of activity. The operation can be recommended for chronic lateral ankle and subtalar joint instability.