In thirty elbows that had an established non-union of a fracture of the lateral humeral condyle that had occurred more than five years before, treatment consisted of one of three operations: anterior transposition of the ulnar nerve (nine patients), corrective osteotomy of the humerus and anterior transposition of the ulnar nerve (four patients), or osteosynthesis of the non-union combined with neurolysis and anterior transposition of the ulnar nerve, with or without corrective osteotomy of the humerus (seventeen patients). Of the thirty patients, fifteen had been apprehensive when using the elbow, due to lateral instability, or had had pain in the elbow. In thirteen of these fifteen patients, the non-union was treated by osteosynthesis. Afterward, the pain and apprehension disappeared, but the range of motion of the elbow decreased in all but three patients. Three patients had clicking between the humerus and radius, and the bone failed to unite in three others. Osteosynthesis is indicated for the treatment of non-union of the lateral humeral condyle only if the patient has serious pain in the elbow or apprehension when using the elbow, due to lateral instability.