The population dynamics of sand flies (Diptera: Psycbodidae) were studied in Sanhurfa province in southeastern Turkey, in the country's largest focus of typical anthroponotic cutaneous leishmaniasis, during 2000-2002. Sand flies were collected at nine different sampling stations, located throughout the city, representing a cross section of urban and rural habitats. In total, 29,771 sand flies were collected, 45.35% of which were Phlebotomus papatasi Scopoli. In this study, the overall sand fly species diversity, relative abundance of each species, biodiversity, and similarity indices among sampling stations and efficiency of trapping methods were evaluated. Among the sampling stations, Sanhurfa city center and Suruc were shown to have the highest number of sand fly species; Harran-Akcakale and Hilvan habitats produced the largest number of individuals. The greatest similarity rates (80%) in terms of sand fly species were observed between Hilvan and city center, Harran-Akcakale and city center, Harran-Akcakale and Yenice, and Siverek and Viransehir. The lowest similarity rate (16%) was observed between Bozova-Birecik and city center. Comparison of biodiversity and similarity indices between the various sampling stations reveals the distribution of the suspected vector species and provides basic knowledge required to develop logical and effective control strategies. Among the trapping methods used, light traps showed the highest capture efficiency, above aspirators and sticky papers. It was concluded that light traps alone were sufficient to determine the sand fly fauna of the study area. It is recommended that the spatial and temporal dynamics of sand fly populations be monitored throughout the southeastern Anatolia Project (GAP) construction period, considering the potential impact the project may have on mean temperature, humidity, and human population movements.