Aqueous extracts of fresh leaves of Daphne gnidium and Peganum harmala were evaluated in the laboratory for their insecticidal effect on mosquitoes larvae, Culex pipiens (Diptera; Culicidae) at 75 g/l, 150 g/l et 300 g/l for D. gnidium and P. harmala. A synergistic effect of extracts from these plants was determined in this study. Our results show that an ingestion treatment provokes an important mortality of the larvae; 100% larval mortality could be obtained using the higher concentrations. Toxicity tests were used to determine the lethal concentrations and lethal times (LC50%, LC90%, LT50% and LT90%).