Out of 87 displaced supracondylar fractures of the humerus in children, 17 were treated by open reduction and internal fixation, in eight cases because of vascular complications (with or without neurological complications) and in nine cases after unsatisfactory closed reduction. In the eight cases with vascular impairment, evacuation of the haematoma, reduction of the fracture and division of the fascia of the forearm caused a return of the radial pulse. Median nerve paralysis, in the four cases with neurological complications as well, recovered within 7 months. Fractures fixed with one pin only redislocated and needed an additional reduction--this procedure was associated with impairment of the range of motion. In spite of the selection of the most severe cases for surgery, the end result was excellent in all cases expect one and considerably better than previous results of closed reduction. Rotational deformity, however, did not decrease with age and growth.