Collagen-platelet interaction, occurring in hemostasis but also a cause of thrombosis, is a two-step process of adhesion and activation involving the sequential recognition of distinct receptors. Adhesion involves first the reversible recognition of collagen-bound von Willebrand factor by the platelet receptor complex Gp lb/IX/V, followed by direct interaction between collagen and the platelet integrin receptor α2β1, which binds to specific sequences in collagen in which the GER motif appears important. Platelet activation then follows from the recognition by the receptor Gp VI of GPP* sequences in collagen, culminating in signalling events unique to collagen as a platelet agonist: Gp VI leads via the novel platelet Fc receptor γ-chain to p72syk and phospholipase Cγ2.