The GP Ib-IX complex is part of a conglomerate of polypeptides on the platelet surface that perform several key roles of central importance to the haemostatic function of platelets. When deranged, these interactions can also lead to pathological thrombosis, with potentially disastrous consequences for the organism. In this manuscript, several aspects of the structure and biology of the complex are reviewed, including the structures of its polypeptides and their relationships to other members of a phylogenetically widespread protein family, its topology on the platelet membrane and relationship with cytoskeletal components, peptide sequences involved in binding its ligands, von Willebrand factor and thrombin, its polymorphisms, its biosynthesis, and the organizations of the genes that encode its subunits.