The aminopyrine breath-test (ABT) has been proposed as a non-invasive quantitative test of liver function and reserve. To evaluate its usefulness, we compared the ABT with standard liver function tests, Child's classification of liver disease and ICG clearance, as means of assessing liver function in 30 patients with cirrhosis. The cumulative output of 14CO2 in breath during the 6 h following [14C]aminopyrine administration was significantly decreased in the cirrhotic group as compared with control subjects. The severity of liver dysfunction, as assessed by Child's classification, was associated with a progressive and statistically significant impairment of the ABT. There was a good correlation between the ABT and ICG systemic clearance (r = 0.770, P less than 0.001) and also between the ABT and ICG intrinsic clearance (r = 0.885, P less than 0.001), a measure which is independent of hepatic blood flow variations. These results further strengthen the concept that the ABT is a simple non-invasive method to assess quantitatively liver function and reserve, and could be useful in following the evolution of patients with liver disease.