Charts of nine patients with Duchenne and one with Becker's muscular dystrophy who had undergone spinal fusion and Harrington rod insertion for scoliosis were reviewed retrospectively. The mean age was 15 years and mean angle of scoliosis was 69 degrees. Preoperative pulmonary function studies showed a restrictive defect with a mean vital capacity of 1.3 +/- 0.69 litres, 35 +/- 20 per cent of predicted value, 33 +/- 20 ml . kg-1 and a mean inspiratory capacity of 0.99 +/- 0.5 litres, 23 +/- 13 ml . kg-1. There were no anaesthetic complications during operation and obstructive cardiomyopathy, hyperpyrexia, hyperkalaemia and rhabdomyolysis were not problems. Succinylcholine was avoided. One patient developed an arrhythmia postoperatively and one patient whose postoperative problems included tracheostomy, pneumonia and sepsis could not be weaned from the ventilator and died 11 weeks after operation. As assessing risk and survival of the operation depends on objective pulmonary function, a vital capacity of at least 20 ml . kg-1 in the range of 30 per cent of predicted volume with an inspiratory capacity of at least 15 ml . kg-1 would appear to be adequate in patients with muscular dystrophy requiring Harrington rod insertion. Other factors including the rapidity of progression of the muscular disease, other respiratory and cardiovascular problems, and disease such as obesity should also be considered.