The relationship between systemic and renal hemodynamics was studied in 20 patients with advanced cirrhosis of the liver. Cardiac output was assessed by an indicator dilution technique, and both mean renal blood flow and intrarenal blood flow distribution were determined by the 133Xe washout method. Ten patients had elevated cardiac outputs (7.14 to 13.58 L/min; HCO group), seven patients had normal cardiac ouptputs (5.16 to 6.78; NCO group), and three had low cardiac outputs (3.65 to 4.1; LCO group). Renal hemodynamics did not correlate with cardiac output (r = 0.051; N.S.), since comparable reductions in mean renal blood flow occurred in both the LCO and HCO patients. Similarly, the degree of cortical ischemia, as assessed by percentage flow to the rapid flow component (C1%), did not correlate with cardiac output (r = 0.007; N.S.). Vasomotor instability as assessed by intrapatient variability of sequential xenon washout studies occurred frequently, and its magnitude did not correlate with cardiac output (r = -0.069; N.S.). These studies demonstrate that the abnormalities of intrarenal blood flow in cirrhosis are independent of alterations in cardiac output. Furthermore, the finding of marked intrarenal hemodynamic instability in the majority of patients with cirrhosis suggests that caution should be exercised in interpreting studies assessing the efficacy of vasoactive agents on renal hemodynamics in this disease, since the changes attributed to treatment may merely reflect spontaneous change.