Human platelets play a crucial role in both haemostasis and its pathological counterpart thrombosis. In order to participate in the haemostatic process, platelets adhere to the site of a damage vascular wall, release a variety of stimulatory mediators (both by exocytosis and following de novo synthesis), provide a pro-coaggulatory surface and express a range of adhesive receptors - all of which culminate in the formation of stable platelet aggregate. A number of patho-physiological compounds can, to varying degrees, elicit this range of platelet responses, notably collagen, thrombin and ADP. Studies carried out over the last decade have helped partially characterize both the platelet receptors, and post receptor signaling pathways, associated with these agonists. The review briefly describes those receptors, and pathways, which have either been conformed, or are believed, to exist in platelets in response to collagen, thrombin and ADP.