A variety of tests has been used to assess liver function and predict hepatic functional reserve in patients with liver disease. These tests comprise clinical assessment, simple biochemical measurements and so-called ‘quantitative’ tests of liver function, ie, elimination rate measurements of exogenous markers such as drugs and other compounds. So far no single test or group of tests has proved to be a sufficiently sensitive and accurate measure of overall hepatic function across the whole spectrum of liver disease. This may he due to diversity in the hepatic handling of these compounds and in changes in architecture, hemodynamics and cell function in liver disease. The absence of a satisfactory test emphasizes the value of clinical assessments (eg, the Child-Turcotte or Child-Pugh classifications), because of their relative simplicity.