During steady state the overall lymphatic return rate of albumin equals the transvascular escape rate of albumin [TERalb, i.e. the fraction of intravascular mass of albumin (IVMalb) passing to the extravascular space per unit time] provided local back-transport is negligible, as previously substantiated in patients with cirrhosis. In nine untreated patients with cirrhotic ascites, TERalb (as determined from the disappearance of intravenously injected radiodinated serum albumin) was on the average 8.5% IVMalb X h-1 (range 4.6-12.7). This value is higher than that of normals (mean 5.9% IVMalb X h-1, range 4.3-7.4, P less than 0.05, one-sided tests). During diuretic treatment TERalb increased to a mean of 13.0% IVMalb.h-1 (range 9.2-22.2), which is significantly higher compared to the untreated state (P less than 0.05) and compared to normals (P less than 0.01). In the untreated condition IVMalb was mean 1.24 mmol (range 0.96-1.64), and this value increased by 20% (P less than 0.01) to an average of 1.49 mmol (range 1.36-1.79) during diuretic treatment. The average increase in IVMalb (0.25 mmol) corresponded to 45% of the intraperitoneal mass of albumin in the untreated state (mean 0.59 mmol), indicating a net transport of albumin from the peritoneal cavity to the plasma during diuretic treatment. The results suggest an increased lymphatic drainage of albumin during diuretic treatment, which may play a role in amelioration of cirrhotic ascites.