Species composition and spatio-temporal abundance of Anopheles (Diptera: Culicidae) larvae and their relationship with environmental variables were studied in an endemic malarious area of northwestern Argentina, where Anopheles pseudopunctipennis is the main vector involved in malaria transmission. From Dec 2001 to Dec 2005, we performed monthly samplings of different aquatic larval habitats, such as puddles, irrigation canals, ponds and pools of Mountain Rivers. To determine the relationship among environmental variables and larval abundance, we used Poisson's regression analysis. We collected 5,079 larvae of which An. pseudopunctipennis was the most abundant species followed by Anopheles argyritarsis and Anopheles evansae. The density of Anopheles pseudopunctipennis larvae fluctuated between the end of spring until autumn, when malaria cases occur in the area. Concurrently, the larval densities of the other anophelinae species fluctuated throughout these climatic seasons. Poisson regression revealed that an increase of mean minimum temperature produced an increase in the abundance of An. pseudopunctipennis and An. argyritarsis. The mean maximum temperature and the water temperature greatly influenced the abundance of An. pseudopunctipennis, An. evansae and An. strodei. Increases of these temperature variables produced increases in abundance of these species. These factors should be taken into consideration when control measures for immature mosquitoes are implemented to reduce the number of larval habitats and the production of larvae, which may ultimately result in the elimination of malaria in this area.