Hereditary haemolytic anaemia not associated with spherocytosis, ovalocytosis, stomatocytosis or haemoglobinopathy was observed in three members of a kindred. There were no demonstrable abnormalities of enzymes of the Embden-Myerhof pathway, the hexosemonophosphate shunt, or of a variety of non-glycolytic enzymatic activities assayed in patient erythrocytes. In each case, red cell glutathione was increased in concentration three to six standard deviations above our normal mean. Erythrocyte glutathione was normally stable and all sulfhydryl reacting material was shown by specific enzyme assays to represent either reduced (97%) or oxidized (3%) glutathione. No abnormality in active transport of oxidized glutathione was demonstrable in the red cells. This syndrome of unknown actiology was transmitted in autosomally dominant fashion or, alternatively, as a possibly x-chromosome linked disorder. Existing data did not permit the differentiation of these two possibilities.