Severe hereditary haemolytic anaemia related to pyruvate kinase deficiency occurs in Basenji dogs homozygous for this autosomal recessive defect. In the current study, three anaemic dogs were treated by total body irradiation and marrow transplantation from non-anaemic histocompatible littermates with resultant complete correction of their haemolytic anaemia. The possible use of marrow transplantation for life-threatening haemolytic anaemias in man is discussed.