In order to assess the role, if any, of atrial natriuretic peptide (ANP) and hemodynamic changes in diuretic response to concentrated ascitic fluid reinfusion (CAFR) in cirrhotic patients, we studied 10 patients with liver cirrhosis before and after aspiration, concentration and intravenous reinfusion of their ascitic fluid. Basal ANP levels were higher than in normal subjects, but not related to the degree of water and sodium excretion. CAFR induced a variable degree of ANP changes and diuretic response, and these two parameters were strictly correlated to each other. No major changes of cardiac output and systemic vascular resistances were observed after CAFR. In conclusion, the apparent resistance to ANP diuretic action observed in basal condition in cirrhotic patients seems to revert after expanding blood volume by CAFR.