This paper presents a brief overview of our current understanding of the relation between plasma macromolecules and atherogenesis. Plasma proteins enter normal intima by vesicular transport across normal endothelium, and convective transport within the intima; accumulation depends mainly on molecular size and the molecular sieve properties of the internal elastic lamina. Within the intima the proteins may be modified; particularly striking changes occur in high density lipoprotein (HDL) and in fibrinogen. Fibrinogen appears to be converted to fibrin which is then lysed, providing a continuing source of fibrin degradation products (FDP). Fibrin also seems to be associated with a tightly bound, plasmin-releasable apo-B-containing lipoprotein; work in progress suggests that much of this fraction is accounted for by lipoprotein(a).