Summa yThe mucopolysaccharidoses present many potential difficulties to the anaesthetist. A review was undertaken of the last 10 years' experience at a paediatric hospital which has a special interest in the treatment of these conditions using bone marrow transplantation. Thirty-five patients underwent 150 general anaesthetics. There was a high incidence of airway problems and cardiorespiratory disease. Laryngoscopy and tracheal intubation was difficult in 40% of patients with Hurler's syndrome and 71% of those with Hunter's syndrome. A tracheal tube of smaller than predicted internal diameter was commonly required. Cardiorespiratory problems included both myocardial and valvular disease which could often be identified preoperatively as could kyphoscoliosis. The implications for anaesthesia are discussed.