Abstract: Four commercial pyrethroid–based insecticides, cypermethrin, fenvalerate, Killer and Tyfon super 20 were tested as larvicides against a laboratory strain of Culex pipiens and kerosene and Tween 80 1% in kerosene were tested as larvicides and pupicides against the same population. LC50 values of tested pyrethroids were 0.00029 ppm (Cypermethrin), 0.026 ppm (fenvalerate), 0.012 ppm (Killer) and 0.014 ppm (Tyfon super 20). The diagnostic concentrations for cypermethrin and Tyfon Super 20 were 0.015 and 0.07 ppm, respectively. LD50 values for larvae were 33.42 and 13.11 L ha-1 and for pupae 69.74 and 36.1 L ha-1 for kerosene and T 80 in kerosene, respectively. The results showed that the mixture of kerosene + T 80 could be used as an effective larvicide and pupicide at much lower rates of application compared to kerosene alone, which reduces the environmental pollution to a great extend.