ALTHOUGH the first description of massive hydrothorax occurring in a case of cirrhosis of the liver has been attributed to Laennec, it has since received scant clinical attention. As a result, its development frequently transforms an otherwise obvious case of cirrhosis of the liver into a puzzling diagnostic problem. It has been cited by Vedel and Puech1 as occurring in 8 to 9 per cent of all cases of cirrhosis of the liver. However, these authors arrived at this relatively high incidence by the inclusion of cirrhotic patients having tuberculous or cardiac pleural effusions. Few reports are available in which the complicating causes for hydrothrax have all been demonstrated to be absent. Gaffart2 and Benedetti3 each reported a small series of cases of cirrhosis with hydrothorax and attempted to exclude the more usual causes of hydrothorax. Christian4 reported a case of hydrothorax on the left side