Ashby's work on the effects of KCl and NaCl on the resistance to hypotonic hemolysis of K•-rich and K•-poor erythrocytes has been repeated with great attention to purity of materials and refinement of technique. The results fail to agree with those of Ashby. 1. KCl produces greater loss in resistance to hypotonic hemolysis than does NaCl, irrespective of the species of the animal from which the cells are taken. 2. While cases of an increase in resistance have been encountered in my experiments, they are either very slight, or else the particular determination is subject to very great uncertainty. The great increases in resistance found by Ashby are not even approached in any of the present series of experiments. 3. Ashby's generalization that KCl and NaCl have opposite effects on red blood cells, and that the sense of these effects depends on whether the cell is K•-rich or K•-poor is not substantiated.