AbstractBile acid kinetics and biliary lipid composition were determined in seven subjects with primary dysbetalipoproteinaemia. They were all homozygous for the apolipoprotein E isoform E‐2 and six of them were hyperlipidaemic (type III hyperlipoproteinaemia). With or without hyperlipidaemia, the apo E‐2/2 phenotype was associated with increased bile acid formation (mean increase compared with 32 normolipidaemic controls, 43%;P<0·025). The biliary lipid composition was not different from that seen in the controls. The results indicate that the uptake by the liver of apo E‐containing remnant particles is of importance for the regulation of hepatic cholesterol metabolism in man. It is suggested that hepatic cholesterol synthesis is stimulated in dysbetalipoproteinaemia, and that this leads to a compensatory increase in bile acid syn