Accumulating evidence from epidemiological and clinical studies suggests that vascular risk factors may be involved in Alzheimer disease (AD). Although the precise contribution of vascular disturbances to the pathogenesis of AD is still unclear, various biochemical and neuropathological data strengthen the view that cerebrovascular deficiencies such as reduced blood supply to the brain and disrupted microvascular integrity in brain parenchyma play a direct or intermediate role in the chain of events ending with a dementia syndrome. The present review focuses on platelet abnormalities and hemostatic alterations in AD. In particular, data from our group, along with current literature, are discussed with regard to the evidence of platelets amyloid precursor protein (APP) processing disturbances in early AD as well as to the recent observations of increased serum levels of thrombomodulin and sE-selectin, which are sensitive markers of endothelial dysfunction. These findings strongly indicate that platelet dysfunction and microvasculature deficiencies occur rather early during the course of AD, thus suggesting a further link between AD-related processes and vascular disorders.