Dehydrated hereditary stomatocytosis (DHSt) is an inherited haemolytic anaemia associated with increased red cell membrane permeability to Na(+) and K(+). It is increasingly recognized that a syndrome of self-limiting perinatal ascites can accompany the haemolysis. The cause of the perinatal ascites is unknown, and it has been argued that this could be due to cardiovascular, hepatic or lymphatic problems. We describe the case of a 16-year-old girl who presented neonatally with abnormal liver function tests and ascites. She was extensively investigated at that time. A liver biopsy showed hepatitis and fatty changes. Her ascites resolved within 6 months. At the age of 15 years, she developed an episode of acute haemolysis and was re-investigated. A diagnosis of DHSt was made. Pseudohyperkalaemia, due to ex vivo loss of K(+) from red cells, was present. This study confirms the previously noted association of DHSt, pseudohyperkalaemia and perinatal ascites, and suggests that the latter is of predominantly hepatic origin.