Effects of 0.001, 0.010, 0.050, 0.100, 0.500 ve 1.000 ppm concentration of malathion, an organophosphated insecticide, on longevity, egg pruduction and hatchability of adult female of the hymenopterous endoparasitoid Pimpla turionellae L. were investigated. The tested concentrations of malathion were administreted orally in a chemically defined synthetic diet. The highest level of malathion caused 100% mortality in 24 hours whereas the insects survived approximately 2.75 and 3.75 days in the 0.500 and 0.100 ppm concentrations of malathion respectively. Diets which contain 0.050 and 0.010 ppm concentrations of malathion significantly decreased longevity and total egg production of the females. Although 0.001 ppm concentration of malathion did not affect the longevity of the insects, it increased total egg production significantly which approximated to about 50%. None of the malathion concentrations tested show any significant effect on percentage of egg hatch in P. turionellae females.