Extracellular water (EWC; 82-bromide), total body water (TBW; 3-THO), intracellular water (ICW = TBW-ECW), plasma volume (PV; 51-Cr), and total body potassium (TBK; 40-K) were studied in patients with cirrhosis of the liver (n = 12) and in controls (n = 12). ECW (39%), TBW (28%), ICW (19%), and PV (24%) increased, TBK (28%) however, decreased in cirrhosis. The results indicate that it is less the lean body mass, but rather the intracellular potassium concentration that is lowered (cirrhosis: 84 +/- 21 mmol/l ICW; controls: 115 +/- 23 mmol/l ICW). Decreased potassium per cell (mmol) and increased intracellular water are discussed as possible reasons for this. The correlation between TBK (%) and serum potassium (mmol/l) was found to be r = 0.56 (p less than 0.002). Correlations between the biochemical parameters gamma-globulins, cholin esterase, serum sodium and serum albumin (g/l PV) and characteristic fluid disturbances in cirrhosis are highly significant whereas albumin (g/kg bodyweight) was the same in both groups. We can support the 'overflow theory' of ascites formation.