To measure the effects of cirrhosis on amino acid (AA) flux and to assess the value of the central plasma clearance rate of amino acids (CPCR-AA) as a hepatocyte function test, 35 patients with cirrhosis were studied before and after operation. Fourteen of these patients died after the operation. CPCR-AA measures the number of milliliters of plasma cleared of AA per minute by the liver and other visceral tissues. It is the ratio of AA entry rate into plasma (from peripheral tissues plus infusion) to the arterial AA plasma concentration. Preoperative CPCR-AA measurements in 21 fasted patients with cirrhosis who were not infected revealed a pattern of AA plasma concentration and exchange similar to that previously observed in patients with sepsis with normal liver function. Whereas the concentration of AA in both groups was slightly lower than normal, the CPCR-AA of each was more than four times that of normal postabsorptive people (p less than 0.01). However, preoperative values of CPCR-AA in patients with cirrhosis who survived was 220 +/- 26 ml/M2/min while that in those who died was 97 +/- 16 ml/M2/min (p less than 0.001). Postoperative measurements remained relatively unchanged: survivors 212 +/- 24 ml/M2/min and those who died 89 ml/M2/min (p less than 0.0005). Measurements in vitro of the hepatic protein synthetic rate in liver biopsy specimens taken at operation correlated well with CPCR-AA values obtained immediately before operation in 10 patients (r = 0.73; p less than 0.01). Thus in patients with cirrhosis visceral amino acid uptake and hepatic protein synthesis are maximally stimulated. Nevertheless, if the preoperative CPCR-AA does not approach the value of 284 +/- 76 ml/M2/min previously observed in patients with sepsis who recover, the patient with cirrhosis is prone postoperatively to die of overwhelming infection and multisystem failure.