Abstract: Toxicity of neem extract (RB-a) against Anopheles stephensi (Mosquito) and Aphanius dispar (Killifish) was studied. The applied concentration of RB-a against Aphanius dispar were 20,30,40,50 and 60 ppm, while the mortality percent was 6.67, 36,67,53.33,80 and 90% respectively. The LC50 was found to be 36.37 ppm and LC90 was found to be 61.04 ppm. The applied concentrations of RB-a were 30,60,90,120 and 150 ppm against Anopheles stephensi, the mortality percent were observed as 15,40,60.80 and 85% respectively. The LC50 against this pest was found to be 69.4 ppm and LC90, was found to be 182.77 ppm.