„Insecticides are an important tool for controlling insect vectors of microorganism pathogens. The aim of this study was to determine the diagnostic dosages of deltamethrin and lambdacyhalothrin for the sand fly Lutzomyia evansi (Nunez-Tovar), a vector of Leishmania infantum in Colombia. Sand flies were collected in the Estacion Experimental de Fauna Silvestre of Coloso, Sucre, a natural reserve that had not been previously treated with insecticides. Glass bottles were used for bioassays, following the simplified method (CDC) for detecting insecticide resistance. Wild females of L. evansi were exposed to different concentrations of insecticides during a test period of 80 minutes. The diagnostic dosages of deltamethrin and lambdacyhalothrin were established in 0,0007%, and 0,00035%, respectively, and the resistance threshold was calculated to be ten minutes for both insecticides, exposure period during which the mortality reached 100%. The time-mortality data suggest that lambdacyhalothrin have a lethal effect on L. evansi at a lower concentration than deltamethrin. The last insecticide was less toxic than lambdacyhalothrin.