The familial hyperchylomicronaemia syndrome is a hereditary disorder of lipoprotein metabolism caused by lipoprotein lipase (LPL) deficiency, apolipoprotein(apo) CII deficiency or LPL inhibition. This syndrome, which is characterized by hyperchylomicronaemia, attacks of epigastric pain, recurrent pancreatitis and the presence of eruptive xanthomas, may ultimately lead to necrotizing pancreatitis or pancreatic insufficiency. Treatment consists of lifelong adherence to a low-fat diet to prevent hyperchylomicronaemia and its sequelae. We describe here the clinical course of a patient with acute pancreatitis due to hyperchylomicronaemia based on hereditary LPL deficiency. The different causes of the familial hyperchylomicronaemia syndrome and its therapy will be discussed and an update is presented of our knowledge concerning the basic molecular defects of this hereditary disorder.