The present report describes a Chinese male who presented for the first time with recurrent encephalopathy and hyperammonaemia at the age of 52 years. He was found to have citrullinaemia. To our knowledge, this is the first Chinese with citrullinaemia and the first non-Japanese who has the variant form of presentation. The patient also has the longest asymptomatic period for citrullinaemia so far described. The patient's biochemical derangement, clinical features and the postulation of his late presentation are discussed. It is noteworthy that simple therapeutic measures, such as lactulose and dietary protein restriction, controlled his symptoms well.