We studied the interrelationships between systemic hemodynamics, sodium excretion and the renin-angiotensin system in 28 nonazotemic cirrhotic patients on a sodium restricted diet. Renal hemodynamics were also assessed. The patients were divided into three groups. Group A comprised 9 patients without ascites or edema; group B comprised 8 patients with ascites and relatively high sodium excretion (41.9 +/- 12.9 mmol/day); and group C comprised 11 patients with ascites and very low sodium excretion (4.8 +/- 12.9 mmol/day). There were no significant differences in urine flow, glomerular filtration rate or effective renal plasma flow between the three groups of patients, although renin and aldosterone levels were significantly increased in group C. Groups A and B did not differ in hemodynamic parameters and no differences were found between the three groups in heart rate or in plasma volume. Group C, however, showed significantly higher cardiac index and lower arterial pressure and systemic vascular resistance. Plasma volume was inversely related to systemic vascular resistance, and natriuresis correlated significantly with both cardiac index (inversely) and systemic vascular resistance (directly). In addition, renin and aldosterone levels were inversely correlated with both mean arterial pressure and systemic vascular resistance. The systemic hemodynamic disturbances in nonazotemic cirrhotics is paralleled by the impairment in sodium homeostasis, suggesting that the decrease in systemic vascular resistance is the primary event leading to hypotension, high cardiac output and the activation of the renin-angiotensin system in these patients.