A 17-month longitudinal malaria survey was carried out in Sainte Marie Island, on the East Coast of Madagascar, from November 1988 to March 1990. During 706 man-nights of captures, 46401 mosquitoes belonging to 32 species were caught. Sporozoïte rates were calculated by Elisa. The malaria vectors were Anopheles gambiae sensu stricto, An. funestus and An. mascarensis. An. gambiae was the main vector. It was highly anthropophilic and partially exophilic. Transmission by this species mainly occurred from November to April, monthly sporozoïte antigene positivity rate varied from 0 to 3.85. The annual inoculation rate was about 100 infecting bites per man, in which 92 by Plasmodium falciparum. An. funestus intervened weakly in transmission. An. mascarensis, a malagasy endemic region anopheline is a newly discovered vector. The observed sporozoïte rate varied from 0.4 to 0.9 between September and March 1990. Parasite indexes in human fluctuated during the year from 64 to 80%. Because of the high level of transmission, recommendations for inhabitants and tourists are proposed.