A sibship with four cases of hereditary elliptocytic anaemia is described. The condition in this family may have arisen as a mutation in the mother of the sibship; affected members were unable to taste phenylthiocarbamide while normal members were tasters. Experiments with (32)P-orthophosphate in vitro did not show any evidence of biochemical upset as found in hereditary spherocytosis; thus a combination of congenital spherocytosis and elliptocytosis cannot be supported as the cause of the haemolytic state. Clinical evidence of haemolytic disease was accompanied by a tendency to excessive lysis in vitro. Infection may play a part in the precipitation of anaemic crises in this as in other hereditary haemolytic anaemias.