—Lipoprotein retention by vascular extracellular matrix proteoglycans is important in atherogenesis. Proteoglycans bind apolipoprotein (apo)B- and apoE-containing lipoproteins. However, the colocalization of apoA-I and apoE with biglycan in atherosclerotic lesions suggests that vascular proteoglycans also may trap high density lipoproteins (HDLs). Because the major HDL subclasses may be atheroprotective to different degrees, we investigated the role of apoE in mediating HDL₂ and HDL₃ binding to the extracellular vascular proteoglycan, biglycan. ApoE-free HDL₂ and HDL₃ did not bind to purified [³⁵S]SO₄-biglycan, whereas apoE-containing HDL₂ and HDL₃ (HDL+E) did. The extent of binding correlated positively with the apoE content for both HDL₂ and HDL₃, although HDL₂+E had a 3.5-fold higher affinity than did HDL₃+E. ApoE on HDL₃ was cleaved into 22- and 12-kDa fragments, whereas apoE on HDL₂ remained intact. These results suggest that the cleaved apoE on HDL₃ results in diminished biglycan binding of HDL₃+E relative to HDL₂+E. Reducing positive charges on lysine and arginine residues on HDL+E eliminated biglycan binding, suggesting an ionic interaction. Thus, apoE is an important determinant of HDL binding to extracellular vascular proteoglycans and may play a role in HDL retention in the artery wall.