Serum and ascites protein concentration and ascites cell concentration alterations were determined serially during diuresis in 27 patients with uncomplicated liver disease. The total protein concentration in ascites increased from 1.38 2 0.96 g m % to 2.86 +-1.28 g m % (p < 0.001); the serum protein concentration from 6.26 rt 0.81 gm% to 7.24 rt 0.93 gm% (p < 0.001), and the ascites to serum ratio of the total protein concentration from 0.21 2 0.13 to 0.38 rt 0.14 (p < 0.001). The white blood cell (WBC) concentration in ascites increased from 289 rt 179 cells per mm3 to 1,108 2 924 cells per mm3 (p < 0.001). Despite the increase in WBC concentration, the polymorphonuclear cell concentration remained constant (42 f 52 cells per mm3 to 68 rt 96 cells per nun')). Protein concentration of the ascitic fluid greater than 3.0 gm% was demonstrated in 12 patients before completion of diuresis and ascitic fluid WBC concentration was greater than 750 cells per mm3 in 17 patients. Ten of 27 patients eventually developed ascites which had a combination of more than 3.0 g m % total protein concentration and greater than 750 cells per mm3. Ascitic fluid protein and WBC concentrations are not "fixed" at a low level in chronic liver disease since each rose during diuresis. Thus, the interpretation of these parameters must be made with caution in patients following significant diuresis.