This paper reports three cases of heterotopic ossification confined to the posterior aspect of the elbow, with severe limitation of flexion and extension in one and ankylosis in the others. Certain etiological factors are considered and comparisons are made with similar, but not identical, cases reported by others. In all three cases treatment consisted in surgical excision of the posterior mass of bone and anterior capsulectomy. Final motion obtained in flexion and extension was 50 to 165 degrees, 60 to 165 degrees, and 45 to 160 degrees.