Ten consecutive patients (fourteen feet) who had a painful coalition of the middle facet of the talocalcaneal joint with restricted motion of that joint were managed with a resection of the coalition and interposition of a split flexor hallucis longus tendon in 1992, 1993, or 1994. Initial nonoperative treatment of all of the feet had failed. According to the ankle-hindfoot clinical rating system of the American Orthopaedic Foot and Ankle Society, there were eleven excellent results and one good, one fair, and one poor result at a mean of fifty-one months (range, thirty-two to sixty months) after the procedure. Thirteen of the fourteen procedures resulted in considerable relief of pain, an improved range of motion of the talocalcaneal joint, and improved function of the foot. No patient had symptoms or functional impairment of the great toe secondary to the interposition of the split flexor hallucis longus tendon. On the basis of these early results, tendon interposition appears to be an excellent procedure for the treatment of a symptomatic coalition of the middle facet of the talocalcaneal joint after initial nonoperative treatment has failed. The presence of degenerative osteoarthritis in the other facets of the talocalcaneal joint is a contraindication to this procedure. The long-term results have yet to be determined. However, the standardized rating system used in the present study will allow accurate comparison of our results with those of subsequent studies.