Technical Abstract: Reducing populations of phlebotomine sand flies in areas prevalent for human leishmaniases is of ongoing importance to US military operations and civilian populations in endemic regions. Collateral reduction of sand flies or human cases of leishmaniases during pesticide campaigns against vectors of malaria indicate that residuals like DDT can be effective. However, not enough is known regarding the efficacy of the current arsenal of Department of Defense-approved pesticides. We need to know more about the potential for ultra-low volume ULV pesticide applications to control Old World sand fly vectors. In this study we examine the performance of 2 pieces of spray equipment, the Terminator ULV and the Grizzly ULV, with Duet and Fyfanon in four combinations against caged Phlebotomus duboscqi (Neveu-Lemaire) and wild populations of Phlebotomus species in a natural environment in western Kenya. All equipment and Fyfanon are approved and listed by the Armed Forces Pest Management Board, and both pesticides registered with the US Environmental Protection Agency. Caged sand flies were reared from local P. duboscqi and the area has long been studied as a human cutaneous and visceral Leishmania focus. Patterns of mortality across grids of sentinel sand flies showed greater efficacy from the Grizzly ULV sprayer regardless of chemical. Sand fly trapping of wild populations before and after treatments suggests local population suppression from ULV sprays. We discuss the implications of these findings for future military preventive medicine activities and encourage further investigations into the merits of ULV for enhancement of force health protection.