The present study deals with the compatibility of the hematoporphyrin and dimilin against Culex pipiens larvae. The early fourth and second larval instars of C. pipiens were pre treated with dimilin for 24, 48 and 72 hours or prolonged time ( i.e. till pupation) then exposed to the hematoporphyrin for 24 hours before irradiation and vice versa. The larvae were kept in darkness during treatment then were exposed to artificial light ( 380-400Wm_2). It was found to produce higher mortality than if either of them was used alone. In addition the interaction between the hematoporphyrin and dimilin was also more synergistic in the younger instar than in the older fourth instars. Combination of the hematoporphyrin and dimilin provided acceptable control levels when dimilin was applied with 24 hours before the application of the hematoporphyrin before the irradiation. The obtained results showed the possibility of using the hematoporphyrin and dimilin in combinations for controlling Culex pipiens larvae.