Total body potassium (40K) and leucocyte potassium measurements were carried out on 19 patients with stable but decompensated cirrhosis maintained on diuretics for previous ascites. Of 13 patients receiving spironolactone alone none had a total body potassium below the expected lower limit of normal, whereas, of six receiving additional frusemide, two had low values. The results for leucocyte potassium were in agreement and simultaneous measurements of leucocyte magnesium showed a close correlation, those with intracellular potassium depletion also having magnesium depletion. One such patient was treated with magnesium supplements without effect on the potassium, although intracellular magnesium was improved. It is concluded that spironolactone alone is the treatment of choice in the maintenance management of such patients; that additional potassium would be unnecessary; and that additional frusemide should be avoided if possible.