Twenty patients who had been treated with Ilizarov external fixation for a Gustilo grade IIIB supracondylar fracture of the femur were functionally assessed 12 to 52 months after treatment. Fourteen fractures were type C3 and 6 were type C2 according to the AO classification. Fractures were united at an average of 39 +/- 9 weeks. There was a final knee extension deficit of 5 degrees to 10 degrees (12.2 degrees +/- 3.5 degrees) and flexion reached 110 degrees +/- 10 degrees in type C2 and 73 degrees +/- 36 degrees in C3 supracondylar fractures. Forty percent of the supracondylar fractures had 4cm shortening and 40% had 1.5 cm. Pin-track infection occurred in 21%. Half of the C3 fracture cases had problems with pain on walking, needed support and had pain at rest, whereas no patients had difficulty getting out of a chair, going up and down stairs. However, all C2 type fractures had problems with all types of function.