Studies on seasonal abundance of Anopheles (Anopheles) pseudopunctipennis, the main vector of malaria in northwestern Argentina, was carried out in three villages (Aguas Blancas, El Oculto and San Ramón de la Nueva Orán) in Orán County, Salta Province (NW). Adults anopheline mosquitoes were sampled from December 2001 to December 2003, using CDC light traps with CO2, and a mechanical aspirator. Anopheles pseudopunctipennis was the most abundant collected species, followed by Anopheles (Nyssorhynchus) strodei and Anopheles (Nyssorhynchus) argyritarsis. Only Anopheles pseudopunctipennis is incriminated as vector of malaria in northwestern Argentina, but Anopheles strodei and Anopheles argyritarsis are incriminated as potential vectors of the disease in neighboring countries. Anopheles pseudopunctipennis was captured during the whole sample period, but the main peak of abundance was recorded between September and December. These results outstand the importance of conducting specific studies to confirm the most important period for malarial transmission.