A study was undertaken to establish the susceptibility of two recently colonized sand fly species, Phlebotomus perniciosus and P. papatasi to some insecticides. A laboratory colony of P. papatasi, unexposed to insecticides for a period of ten years, was used as reference strain. Bioassay tests were carried out according to the WHO standard protocols based on the mortality rates recorded at different exposure times. Serial (from 1 to 60 min) exposures to DDT 2%, lambda-cyhalothrin 0.06% and permethrin 0.2% were tested on groups of 30 adult sugar-fed female sand flies, for a total of 7,470 specimens. Data were subjected to probit analysis and the susceptibility was calculated at LT50 and LT95 by comparison with the laboratory reference strain. The LT50 values for P. perniciosus were 19.9, 3.2 and 6.9 min, and for P. papatasi 18.0, 7.4 and 11.0 min, using DDT, lambda-cyhalothrin and permethrin, respectively. The results showed that two Italian populations of P. perniciosus and P. papatasi from Campania region and from Rome, respectively, are susceptible to the insecticides tested as compared with the reference strain used.