The activities of lecithin-cholesterol acyltransferase (LCAT) and lipid transfer protein (LTP) were assayed using sensitive radioassay methods in controls (n = 113) and in patients with various liver diseases (n = 72). Plasma LCAT activity decreased with progression of hepatocellular damage. Plasma LTP activity in controls was 216 +/- 68 nmol/mL/h, and there were no significant differences between controls and patients with chronic hepatitis ([CH], 193 +/- 70), compensated liver cirrhosis (LC) with or without hepatocellular carcinoma ([HCC], 197 +/- 48 and 193 +/- 62, respectively), or decompensated liver cirrhosis ([dLC], 182 +/- 65). In acute viral hepatitis, LTP activity decreased significantly; however, the degree of reduction was not as dramatic as that for LCAT. There was no correlation between LCAT and LTP activity both in controls and patients with various liver diseases. LCAT activity was positively correlated with serum albumin (r = .52, P < 0.1) and cholinesterase (r = .37, P < .01) levels, and inversely correlated with serum bilirubin level (r = -.38, P < 0.1); there was no correlation between plasma LTP activity and these parameters of liver function. That plasma LTP activity did not change with hepatocellular damage may indicate that the liver in humans may not be the primary site of LTP production.