The existence of pre-mating and post-mating barriers between Culex pipiens L. populations and the possibility of interbreeding between autogenous and anautogenous mosquitoes were examined. Test mosquito populations were stenogamous with > 83% insemination rates in 20 x 20 x 20 cm cages, regardless of autogeny rates ranging from 10 to 91%. Bi-directional crosses between three geographical populations resulted in > 80% hatch rates, indicating full cytoplasmic compatibility. Both autogenous and anautogenous Cx. pipiens individuals were encountered in the progenies of autogenous or anautogenous female parents. Moreover, more than 75% of field caught females produced mixed progenies. thus, the authors suggest there is no limitation for hybridization between Cx. pipiens mosquitoes in Egypt due to the lack of premating and post-mating barriers.