Ultimately, we seek to understand how saliva of arthropods contribute to the interaction of vectors with vertebrate hosts. Toward this end, we shall investigate anti-hemostatic, vasoactive anti-inflammatory, and immunosuppressive properties of vector saliva, characterizing them both pharmacologically and biochemically. Ixodid and argasid ticks, sand flies, triatomine bugs, and fleas will be included in these studies. In particular, anti-hemostatic studies will concentrate on the antiplatelet activity of Ornithodorus moubata. Vasoactive studies will study further the erythema-inducing factor of Lutzomyia longipalpis, characterize the salivary vasodilator of Rhodnius prolixus, and investigate the erythema-inducing factor of Xenopsylla cheopis. Anti-inflammatory activities will investigate the kininase activity of O. moubata and characterize the LTB immunoreactive material of Ixodes dammini, possibly an LTB antagonist. Immunosuppressive activities will concentrate on the anti-neutrophil activity of I. dammini saliva, as well as its anti-lymphocyte activation property. This work explores the suggestion that saliva of hermatophagous arthropods mainly serves an antihemostatic and antiinflammatory role during blood-finding and blood-feeding. As this idea is further explored, it is our hope more will be learned on the biology of vectors and the parasites they vector, and that novel pharmacological compounds will be found.