The secondary effects emerging from the use of conventional pesticides on environmental and human health were lead scientists to look for other safety products. Natural pesticides are promising in pest control, especially those derived from plants. In this study, the larvicidal activity and their effect on the reproduction potency of the essential oils of Ruta chalepensis and Eucalyptus camaldulensis were evaluated against the mosquito species Culex pipiens. Newly exuviated larvae of third and fourth instar larvae were exposed to various concentrations of Ruta chalepensis (150-700 ppm) and Eucalyptus camaldulensis (100-600 ppm). The results, for both plants, showed a toxic effect of the treated larval series with dose-response relationship. For Ruta chalepensis oil bioassay the lethal concentrations (LC50 and LC90) were estimated at 95ppm and 550 ppm for the third-instar larvae, respectively, while these respective values were 245ppm and 830ppm for the fourth-instar larvae of Culex pipiens. For Eucalyptus camaldulensis oil the LC50 and LC90 values of were 185 and 580ppm for the third-instar larvae, and 280 and 1050 ppm for the fourth-instar larvae respectively. In other experiments the compound was applied at LC50 and LC90 against the fourth instars larvae and its effects was investigated on fecundity of female emerged from larval treated series with lethal concentrations. The results showed that the two oils reduced significantly the laying egg number and the percentage of fecundity.