Twenty-five brain-injured adults who were treated for tardy ulnar neuropathy during a 5-year period were studied. Two patients had bilateral involvement. The incidence of late ulnar neuropathy in this population was determined to be 2.5%. The ulnar neuropathy was always on the neurologically impaired side and associated with significant spasticity. Diagnosis was made when intrinsic atrophy was noted in the hand. No patient initiated a subjective complaint. Nerve conduction velocity measurements confirmed impingement of the ulnar nerve in the cubital canal in 16 cases. Twenty-one of the 27 (78%) elbows had moderate to severe heterotopic ossification causing impingement of the ulnar nerve. All patients were treated by anterior transposition of the ulnar nerve. Follow-up averaged 22.7 months. Twenty-three (85%) extremities had complete recovery of ulnar nerve function. Four patients had improved but incomplete recovery of function. Prolonged compression of the nerve led to incomplete recovery.