Lipoprotein lipase (LPL) activity in postheparin plasma of 38 normolipidemic volunteers was related to the magnitude of postprandial lipemia after a fat meal, to triglyceride content of high density lipoprotein2 (HDL2), to hepatic lipase (HL) activity, and to HDL2 levels. LPL activity correlated indirectly with lipemia, triglyceride content of HDL2, HL activity, and levels of HDL2 but not of HDL3. HL activity correlated directly with lipemia and indirectly with HDL2 levels. Triglyceride content of HDL2 correlated directly with lipemia and indirectly with HDL2 levels. In HDL2, abundance of apolipoprotein (apo) A-II and the apoA-I/apoA-II ratio varied widely. The latter correlated positively with LPL activity and HDL2 levels, and, inversely, with HL activity, lipemia, and triglyceride content of HDL2. The study suggests that HDL-cholesterol is not an independent parameter of lipid transport, but is strongly affected by triglyceride metabolism through lipolytic enzymes, as exemplified by postprandial lipemia that affect both composition and plasma levels of HDL2.