Hematophagous arthropod association with vertebrates probably evolved from close association with vertebrate nests or from adaptations of fruit eating or insectivorous activities by arthropods. These associations are interactive evolutionary forces best examined using multidisciplinary approaches. Papers in this symposium examine some of the progress made in this area and suggest future direction for basic and applied research on the physiological interactions of hematophagous arthropods and their vertebrate hosts.