1. Sodium transport studies were performed in erythrocytes from normal subjects and from patients with acute myeloid leukaemia. Sodium influx and efflux rates were increased in erythrocytes from leukaemic patients.
2. The ouabain-sensitive component of sodium efflux was increased in leukaemic erythrocytes.
3. The high sodium efflux from leukaemic erythrocytes was decreased when the incubation media contained leukaemic plasma, suggesting the presence of an ouabain-like factor in the plasma. Paired experiments failed to show the presence of a similar factor in normal plasma.
4. Leukaemic erythrocytes showed a significantly greater ouabain uptake than the normal cells.
5. The results are discussed in relation to the widespread electrolyte disturbances in acute myeloid leukaemia.
