Apolipoprotein E concentrations in plasma were investigated in 17 patients with hepatocellular (non-cholestatic) liver disease. Ninety-five per cent of plasma apolipoprotein E was recovered in density fractions less than 1.063 kg/l and it was therefore associated with very low-density lipoproteins (VLDL) and low-density lipoproteins (LDL). Very low-density lipoproteins and LDL apolipoprotein E correlated positively (r = 0.63, p less than 0.01) with plasma bile salt concentrations when a decrease in liver protein synthesis was taken into account. This may be due to a down-regulation of the hepatic apolipoprotein B, E receptors concomitant with increasing plasma bile salt concentrations.