Thirty cases of posterior ankle impingement in 28 patients were treated over a 10-year period (1982-1992). All conditions were caused by forced plantar flexion. An os trigonum or posterior process fracture was demonstrated radiographically in 63% of these cases, and an intact posterior process was demonstrated in 33%. Ten cases were lost to follow-up. Of the remaining 20 cases, in 18 patients 12 (60%) improved with nonoperative treatment; 8 (40%) required operative excision. The results were good to excellent in 7 patients and fair in 1 patient. Operative excision for the treatment of recalcitrant posterior ankle impingement can relieve symptoms and allow a return to full preinjury activities.