Four populations of the phlebotomine sandfly Phlebotomus (Phlebotomus) papatasi (Scopoli) (Diptera: Psychodidae), in different ecoregions at altitudes between 368 and 1117 m in the Sanliurfa Province of Turkey, were compared using morphometric and isoenzyme analyses. A similarity phenogram obtained from allozyme data showed that heterozygosity was extremely low, particularly for the alleles which were found to be completely fixed in populations at Hamdun (HMD) and Alitas (ALT). Populations at Akcakale (AKL) and ALT branched as a separate group from populations at Hayatiharrani (HHR) and HMD. The ALT population at the highest altitude (1117m), and the HHR population (488 m) were clustered distinctly when linear measurements of 46 morphological characteristics were examined. A UPGMA (unweighted pair-group method using arithmetic averages) phenogram also showed that ALT and HHR clustered separately, whereas AKL and HMD formed another group.