Objective:To investigate species composition,density,accumulated degree-day and diversity of sand flies during April to October 2010 in Azarshahr district,a new focus of visceral leishmaniasis in north western Iran.Methods:Sand flies were collected using sticky traps biweekly and were stored in 96%ethanol.All specimens were mounted in Puri’s medium for species identification using valid keys of sandflies.The density was calculated by the formula: number of specimens/m of sticky traps and number of specimens/ number of traps.Degree-day was calculated as follows:(Maximum temperature + Minimum temperature)/2—Minimum threshold.Diversity indices of the collected sand flies within different villages were estimated by the Shannon- weaver formula(H’=sum form(i=1) to s Pi log_e Pi ).Results:Totally 5 557 specimens comprising 16 Species(14 Phlebotomus,and 2 Sergentomyia) were indentified.The activity of the species extended from April to October.Common sand-flies in resting places were Phlebotomus papatasi, Phlebotomus sergenti and Phlebotomus mongolensis.The monthly average density was 37.6.41.1, 40.23,30.38 and 30.67 for Almalodash,Jaragil,Segaiesh,Amirdizaj and Germezgol villages, respectively.Accumulated degree-day from early January to late May was approximately 289 degree days.The minimum threshold temperature for calculating of accumulated degree-day was 17.32℃.According on the Shannon-weaver(H’),diversity of sand flies within area study were estimated as 0.917,1.867,1.339,1.673,and 1.562 in Almalodash,Jaragil,Segaiesh,Amirdizaj and Germezgol villages,respectively.Conclusions:This study is the first detailed research in terms of species composition,density,accumulated degree-day and diversity of sand flies in an endemic focus of visceral leishamaniasis in Azarshahr district.The population dynamics of sand flies in Azarshahr district were greatly affected by climatic factors.According to this study the highest activity of the collected sand fly species occurs at the teritary week of August.It could help health authorities to predicate period of maximum risk of visceral leishamaniasis transmission and implement control program. Objective: To investigate species composition, density, accumulated degree-day and diversity of sand flies during April to October 2010 in Azarshahr district, a new focus of visceral leishmaniasis in north western Iran. Methods: Sand flies were collected using sticky traps biweekly and were stored in 96% ethanol.All specimens were mounted in Puri’s medium for species identification using valid keys of sandflies. density: calculated by the formula: number of specimens / m of sticky traps and number of specimens / number of traps. Decree-day was calculated as follows: (Maximum temperature + Minimum temperature) / 2-Minimum threshold. Diversity indices of the collected sand flies within different villages were estimated by the Shannon-weaver formula (H ’= sum form (i = 1) to s Pi Log_e Pi). Results: Totally 5 557 including 16 Species (14 Phlebotomus, and 2 Sergentomyia) were indentified. The activity of the species extended from April to October. Common sand-flies in resting places were Phlebot omus papatasi, Phlebotomus sergenti and Phlebotomus mongolensis. The monthly average density was 37.6.41.1, 40.23, 30.38 and 30.67 for Almalodash, Jaragil, Segaiesh, Amirdizaj and Germezgol villages, respectively. Acccumulated degree-day from early January to late May was approximately 289 degree days. The minimum threshold temperature for calculating the accumulated degree-day was 17.32 ° C. Based on the Shannon-weaver (H ’), diversity of sand flies within area study were estimated as 0.917, 1.867, 1.339, 1.673, and 1.562 in Almalodash, Jaragil, Segaiesh, Amirdizaj and Germezgol villages, respectively. Conclusions: This study is the first detailed research in terms of species composition, density, accumulated degree-day and diversity of sand flies in an endemic focus of visceral leishamaniasis in Azarshahr district. The population dynamics of sand flies in Azarshahr district were greatly affected by climatic factors. According to this study the highest activity of the collected sand fly species occurs at the teritary week of August.I could help health authorities to predicate period of maximum risk of visceral leishamaniasis transmission and implement control program.