Inherited defects of platelet function are a heterogeneous group of disorders that can result in bleeding symptoms ranging from mild bruising to severe mucocutaneous haemorrhage. These defects may be classified according to their effect on the various steps of platelet microthrombi formation including initiation, extension and cohesion, or based on their particular structural or functional deficiency. Platelet membrane receptor deficiencies result in the rare, but well-characterized syndromes of defective clot initiation, such as Bernard-Soulier Syndrome. Platelet storage pool defects are the most common disorders affecting the extension phase of clot formation. Glanzmann thrombasthenia, with absent or dysfunctional alpha IIb beta 3 receptor is the prototypical defect of the cohesion/aggregation phase of microthrombi formation. Many of these disorders share common treatments although some therapies will have greater efficacy for one patient than another and should be individualized so as to provide optimal control of symptoms. Currently much effort is being put into methods to more rapidly and accurately diagnose patients with platelet disorders and to initiate appropriate therapy and prevent life threatening bleeding.