Adhesion of platelets to the subendothelial matrix of an injured vessel wall is an essential step in triggering the formation of a haemostatic plug. Fibronectin, collagen and laminin are three major components of the subendothelial matrix which support platelet adhesion¹. Receptors for fibronectin and collagen have been identified on platelets and are included in the integrin family^2–11. Here we report that adhesion of platelets to laminin is inhibited by a rat monoclonal antibody against the integrin family member, VLA-6. This antibody does not affect platelet adhesion to fibrinogen, fibronectin or to type I and III collagen. Binding to laminin does not require platelet activation and is not inhibited by fibronectin and laminin cell-attachment peptides. Platelet adhesion to laminin is supported by Mn²⁺, Co²⁺and Mg²⁺, but not by Ca²⁺, Zn²⁺ and Cu²⁺. This cation preference is distinct from that characteristic for other platelet-adhesive glycoproteins^8,12,13.