Lecithin: cholesterol acyltransferase (LCAT) activity in patients with liver disease has been found to be either normal or lower than normal, but no information on LCAT mass in these patients is available. In this study, LCAT mass concentration together with LCAT activity and cholesterol esterification rate were measured in the plasma of 19 patients with cholestatic liver disease and 21 patients with non-cholestatic liver disease. The LCAT mass in plasma correlated positively with serum albumin (r = 0.69, p less than 0.001) and pre-albumin (r = 0.77, p less than 0.001) and negatively with serum bilirubin (r = -0.42, p less than 0.01) and bile salts (r = -0.43, p less than 0.01), thus reflecting the severity of liver disease and liver protein synthesizing capacity. In plasma, LCAT mass concentration also correlated well with LCAT activity (r = 0.88, p less than 0.001) and cholesterol esterification rate (r = 0.73, p less than 0.001), thereby indicating that the decrease of LCAT activity and cholesterol esterification rate in liver disease is primarily a function of decreased LCAT mass.