A capture-recapture experiment was undertaken in October 1987, in the Jaru district of Rondonia, Brazil, with the malaria vector Anopheles darlingi. On two consecutive nights, 160 blood-fed, 78 unfed biting and 81 unfed resting mosquitoes were released. Recapture rates of 12-19% and survival rates of 0.59-0.57 per oviposition cycle were obtained for all releases, indicating that blood-feeding was not an obstacle for this population, which had a high vectorial capacity. Two A. darlingi were collected 7.2 km from the release site nine days after release. In contrast, recapture rates for 259 anophelines of nine other species released were only 2.3%. These other species also had a limited flight time and range in comparison with A. darlingi, which indicates that the latter is the only malaria vector of importance in this part of Brazil.