SUMMARY A patient is reported with hypobetalipoproteinaemia and clinical features resembling the Bassen-Kornzweig syndrome (abetalipoproteinaemia) more completely than previously described. This supports a link between hypobetalipoproteinaemia and abetalipoproteinaemia and it is suggested that the Bassen-Kornzweig syndrome has a wide spectrum with serum betalipoprotein ranging from absent to normal. It is likely that there are different genetic entities with similar end results.Absent serum P-lipoprotein (abetalipoproteinaemia) is usually associated with the Bassen-Kornzweig syndrome (Bassen and Kornzweig, 1950) which, in its complete form, is characterised by a Friedreich's type ataxia, acanthocytosis, steatorrhoea, fat-loading of the small-intestinal enterocytes, and atypical retinitis pigmentosa.