Valvular disease in mucopolysaccharidosis type I-Hurler (MPS/1H) is relatively common, but mitral stenosis is very rare in this genetic abnormality. The authors describe the case of a 16-year old girl with Hurler's syndrome diagnosed at 4 years of age. The morphological features were characteristic: bridged nose, thickened lips, macroglassia, short neck (gargoylism, short, thick fingers and limitation of brachial and fore-arm flexion. She presented with stage II dyspnoea and paroxysmal nocturnal dyspnoea. Radiological and echocardiographic studies revealed severe mitral stenosis with haemodynamic complications requiring mitral valve replacement. Anatomopathological analysis of the mitral valve confirmed mucopolysaccharide deposits as the cause of this particular case of mitral stenosis.