We used geospatial techniques to study the potential impact of 2 exotic mosquitoes, Aedesalbopictus and Ochlerotatus japonicus japonicus, on the epidemiology of West Nile virus in Maryland. These2 species have established populations in Maryland over the past 15 years. Larvae ofboth mosquito species arefound in natural and artificial water-holding cavities and containers, particularly water in tires. Therefore, weused locations of licensed tire dealers and of tire dumps scheduled for clean up as an index for potential sourcesof mosquito vectors. This index was expected to underestimate the actual population of source habitats. WestNile virus activity in Maryland during 1999, 2000, and 2001 was indicated by the presence of dead, infectedbirds, particularly American crows and other corvids; infected pools of mosquitoes; and human and horseinfections. Adult females of both mosquito species are aggressive, opportunistic feeders that have been observedto take blood meals from avian and mammalian hosts. Susceptible vertebrate hosts, particularly birds, are ubiquitouslydistributed throughout the developed areas of the state. This analysis demonstrated a spatial convergenceof the virus, the exotic mosquito vectors, and susceptible hosts. This conjunction indicated that these 2 mosquitospecies have a high potential to serve as bridge vectors and thus, impact the epidemiology of West Nile virusunder favorable environmental and climatic conditions. Positive mosquito pools were collected from only theBaltimore-Washington metropolitan corridor suggesting a newly created enzootic focus for this virus. Landcoveranalysis of the sites where virus activity had been detected showed predominantly developed land uses.Analyses of the environmental justice aspects (social, economic, and housing characteristics) of block groupswith human West Nile fever cases or with positive mosquito pools were equivocal. Human cases seemed tooccur in developed block groups with lower income levels.