The borderline of Iran with Azerbaijan, Armenia and Turkey had been considered a malaria free region. However, in 1991, after the independence of the southern countries of the former Soviet Union, a new threat of malaria importation emerged from those countries into Iran, which was affected by serious epidemics of Plasmodium vivax malaria. Various factors can affect malaria resurgence in this region, such as socioeconomic conditions, especially the displacement of massive populations from war-stricken zones in the Republic of Azerbaijan. Accordingly, in some parts of West-Azerbaijan, East-Azerbaijan, Ardebile and Gilan provinces of Iran, several malaria foci were observed. Construction of dams, people traveling from neighboring countries to Iran, urbanization, irrigation projects, lack of malaria vector control, shortage of drug supplies are also major factors in malaria outbreaks in the region. An investigation was carried out on the bionomics of the main malaria vectors in the region. The result showed that Anopheles sacharovi plays an important role in malaria transmission and An. maculipennis and An. superpictus can be secondary vectors. Larvae were found in slow flowing water and channels with water plants. They were more abundant in June. The parity rate of blood-fed females was high in May. An. sacharovi is active from May to October with two peaks of activity, which occur in August and October. The population of this species is higher in animal shelters with a zoophicity of 95%. About 90% of bites took place in the second half of the night. A CDC light trap can also catch this species. Susceptibility testing using the WHO-recommended diagnostic doses of insecticides, revealed that this species is resistant to DDT and dieldrin, but susceptible to malathion, fenitrothion, propoxur, bendiocarb, lambdacyhalothrin, permethrin, cyfluthrin, etofenprox and deltamethrin.