Deltamethrin is one of the most effective insecticides for vector control, already widely used for bednet impregnation to control malaria. To evaluate the efficacy of deltamethrin-impregnated bednets in malaria control and in reducing the biting nuisance caused by Anopheles sacharovi, field trials were carried out in an endemic area of malaria in the surrounding rural settlements of Sanliurfa City, SE Anatolia, Turkey. Preliminary studies commenced in August 1999 with pre-intervention house-to-house surveys to identify villages outside of Sanliurfa City with high malaria incidence, to collect socio-economic, epidemiological and entomological data, and to determine physical properties of the study areas. An intervention field trial promoting the use of K-OTAB (deltamethrin-tablet formulation) impregnated bednets by local inhabitants of four villages was performed between July 2000 and July 2001. Its aim was to examine the monthly and annual efficacy of such bednets in controlling malaria and to compare the effect of impregnated bednets (IB) with non-impregnated bednets (NIB). The experimental design consisted of four villages. Gedik was selected as the intervention area using IBs, Orgulu served as the control area, and in Persiverek and Sandi NIBs were implemented. All 1,406 inhabitants of the 146 households were recruited for the study. Results showed significant (P<0.05) reduction in malaria incidence in Gedik from. 8.29% in the pre-treatment year to 1.57% in the post-treatment year. In contrast, malaria incidence slightly increased in Orgulu from 6.55% to 7.58%. Similar results were obtained from the other two villages where NIBs were used; malaria incidence rates increased from 2.16% to 6.77% (Persiverek) and from 1.9% to 9.8% (Sandi). Entomological surveys, employing different techniques, were carried out randomly at selected collection sites within the intervention and control settlements every month from June 2000 to June 2001 to determine the fluctuation of seasonal population sizes and compare the monthly density of malaria vectors between intervention and control areas.