Apolipoprotein B‐100‐containing lipoprotein assembly is dependent on the successive addition of triglyceride by microsomal transfer protein. Assembly may end at this point and the lipoprotein secreted or it may continue with the bulk addition of triglyceride by an unknown transfer process. These steps are independently regulated and result in the secretion of a spectrum of apolipoprotein B‐100‐containing particles. The production of small, dense LDL is determined by the type of VLDL secreted by the liver. Large, triglyceride‐rich VLDL1 results in the formation of small, dense LDL through triglyceride exchange and subsequent hydrolysis. Small, dense LDL are cleared from plasma relatively slowly and tend to accumulate in the circulation where they exert their atherogenic effects. Curr Opin Lipidol 9:197–202. © 1998 Lippincott–Raven Publishers