Sand flies were infected with different species of promastigotes from reptiles and warm-blooded animals. Optimal doses of promastigotes were used which ensured the adaptation of Protozoa in the host's intestine. The infection with a mixed culture resulted in the death of most Sand flies: the mortality rate was the highest at the simultaneous introduction of two species and was some what lower at the subsequent infection. The survival of Sand flies infected with one species of leishmania decreased to the greatest extent if "incidental" for them strains of promastigotes were introduced: for Ph. papatasi -- cultures isolated from reptiles, for Sergentomyia arpaklensis -- those isolated from L. tropica major. Natural infection rate of the genera Phlebotomus and Sergentomyia with leishmania of different species agrees with laboratory data on the survival of sand flies. Ph. caucasicus and Ph. papatasi are infected, in general, with L. tropica major, S. arpaklensis -- with L. gymnodactyli.