In the past, the major functions of the platelet cytoskeleton have been considered to be those of regulating the shape of the unstimulated platelet and inducing contractile events such as secretion of granules and retraction of clots by activated cells. However, in recent years, the realization that the cytoskeleton can interact with numerous signaling molecules has revolutionized our understanding of the importance of the platelet cytoskeleton in regulating platelet function. An important component of the platelet cytoskeleton in terms of regulating signal transduction is the membrane skeleton. The model that is emerging is that this structure lines the lipid bilayer, interacts with the cytoplasmic domain of transmembrane receptors, and recruits signaling molecules to a submembranous location (Fox, 1996a; Fox et al., 1993a). As platelets are activated, the cytoskeleton reorganizes producing complexes of cytoskeletal proteins that recruit and activate additional signaling molecules. The cytoskeletal reorganizations that occur and the signaling molecules that are recruited vary depending on the conditions of activation.