Vector incrimination studies were conducted from April 2003 to February 2005 at three riverine villages 1.5 km to 7.0 km apart, along the Matapi River, Amapa State, Brazil. A total of 113,117 mosquitoes were collected and placed in pools of <or=7 mosquitoes (19,883 pools) and tested for species-specific circumsporozoite protein (CSP) of P. falciparum, P. vivax VK210, and P. vivax VK247 using the enzyme-linked immunoabsorbent assay (ELISA). A subset of 63,330 mosquitoes (12,191 pools) was tested for P. malariae. Anopheles darlingi and An. marajoara had the highest proportion of circumsporozoite protein positives for human malaria parasites compared with An. nuneztovari, An. triannulatus, and An. intermedius. Anopheles darlingi and An. marajoara had the highest entomological inoculation rates (EIR) and were considered to be the most important malaria vectors in the study. Anopheles nuneztovari was also an important vector. Differences in entomological inoculation rates were more dependent on mosquito abundance than on sporozoite rates.