Malaria has reemerged as a significant public health disease threat in Peru, especially withinthe Amazon Basin region. This resurgence of human cases caused by infection with Plasmodium falciparumand Plasmodium vivax is thought to be associated with the spread of Anopheles dartingi, the principal SouthAmerican malaria vector, into new areas of the Amazon Basin. However, comprehensive studies of the distributionfor this species have not been conducted in Peru for several years, nor are historical accounts accurateenough to determine if An. darlingi was actually present and not collected or misidentified. Therefore, theobjective of this study is to define the distribution of An. dartingi as well as obtain data on distribution andabundance of other Anopheles species in this region. Mosquitoes were collected during 2001 in the Departmentsof Loreto and Ucayali, the two largest Amazonian Departments of Peru. A total of 60,585 specimens representing12 species of the subgenera Nyssorhynchus and Anopheles were collected at 82 (88.2%) of 93 collecting sites.The majority of mosquitoes obtained were identified as An. benarrocftl, comprising 7O:7Eo of mosquitols collected,followed by An. darlingi (24.0%), Anopheles mattogrosensis (2.4%), and Anopheles triannulatus (1.5%).Anopheles darlingi was collected from 48.8% of sites, indicating that this species is established throughoutcentral Loreto, including further west in the Amazon Basin than previously reported. These data suggest thatthis species is now found in areas of the Amazon Basin region where it has not been previously reported.