Hepatopulmonary syndrome--a complication of chronic liver disease-is characterised by hypoxaemia, which results from widespread intrapulmonary vascular dilatations. Amplified production of pulmonary nitric oxide is thought to be important in development of this disorder in patients with liver cirrhosis. Here, we report a 64-year-old man with hepatopulmonary syndrome associated with hepatitis-C-virus-related cirrhosis. We gave the patient nebulised N(G)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthesis, which enhanced oxygenation (arterial oxygen pressure increased from 6.98 to 9.45 kPa). After L-NAME, the distance the patient could walk in 6 min rose by 92 m. Administration of L-NAME by aerosol might offer a new approach to treatment of hepatopulmonary syndrome.