Ecological studies on sand flies were carried out in two villages of the Nile Delta Governorates namely; Kafr Tahla (Qalyubiya) and el-Quantara el-Beida (Kafr El-Sheikh) from September 2003 to August 2005. Sand flies were collected weekly from around houses, stables and near rodent burrows using sticky paper traps. A total of 9529 sand flies were collected from two villages, all of which were identified as Phlebotomus papatasi. Sand flies activity started from April to December with a bimodal annual pattern. The sex ratio of collected sand flies was significantly male biased. Data analyses revealed that sand fly densities were strongly correlated to temperature but not to relative humidity or wind velocity. Variation in the densities of P. papatasi in both villages did not show a significant effect due to lunar phases. However, sand fly activity was highly positively correlated to fraction illumination.