Introduction & Objective: The aim of the study was to identify larval habitats and new species and determine the exact distribution of Culicidae in Hamadan Province.Materials & Methods: This descriptive,cross -sectional study was conducted in six regions of Hamadan Province during 2010. Sampling method was carried out by standard Dipping method. Specimens were mounted by lactophenol solution and were sent to Medical Entomology Laboratory, Tehran University of Medical Sciences with related codes. The accurate diagnosis of Culex pipiens was made with male genitalia morphology. The data were analyzed using standard statistical software (SPSS version 11.5). Results: In total, 4751 larvae of the three genera including Anopheles, Culex, Culiseta ,and nine species including An.superpictus, An.maculipennis sl and An.claviger, Cx.pipiens,Cx.theileri, Cx.hortensis and Cx.prexiguuus ,Cu.longiareolata ,and Cu.subochrea in 36 larval habitat sites in the province were collected and identified. Among Culicidae larvae collected, Culex. Pipiens and Culiseta.subochrea with 58%, and 0.4% of samples were the most and the least species collected. Conclusion: Culex pipiens was reported as the dominant species . Based on morphology of male genitalia, only Culex pipiens was identified among the complex species .The species of Anopheles claviger and Culex prexiguus were found for the first time in this area. The molecular analysis and the egg ridge counts of anopheles maculipennis sl must be extensively studied in the future. (Sci J Hamadan Univ Med Sci 2011;18(3):50-58)