Abstract: Two repellents includes Iranian and Merck dimethyl phthalate (DMP) were evaluated against Anopheles stephensi and Culex pipiens, using American Society for Testing and Material (ASTM) standard ED 951-83 procedure, a free choice method based on the variable dose-fixed time. Also a modified of ASTM method we used for determination of effective dosages of the repellents. In ASTM method there were no significant differences between the two repellents (Iranian and Merck's DMP) as indicated by the ED50 and ED95 values (p>0.05). But, there were significant differences in repellent sensitivity between An. stephensi and Cx. pipiens at the ED95 level. In modified ASTM method there were no significant differences between the two repellents against An. stephensi, as indicated by the ED50 values (p>0.05). But, there are significant differences between the two repellents against Cx. pipence based on ED50 value. Results of this study showed that the Iranian synthesized DMP has necessary potential and specificity to compare with Merck manufactured product.