1. Significant positive correlations were found between the lipoprotein lipase and hepatic lipase activities of post-heparin plasma samples and plasma high-density-lipoprotein (HDL) cholesterol concentrations in 21 children with hyperlipidaemia and six normal adult males.
2. A significant positive correlation was also observed between the two lipase activities and the ratio of HDL cholesterol to apoprotein AI (apo AI) concentrations.
3. These findings provide further evidence that a significant proportion of HDL and possibly the HDL2 subfraction is formed during the clearance of triglyceride-rich lipoproteins.