Significantly more virgin Culex tarsalis females were mated and fully inseminated by unirradiated males than by irradiated males when caged at a ratio of 1 male to 10 virgin females for 10 days. Females caged with irradiated males produced more unembryonated egg rafts than females caged with unirradiated males. Of 38 unembryonated egg rafts deposited by females caged with males irradiated at 5.5 kR, 50% were attributed to inseminated females. There was no difference in the size of egg rafts deposited by inseminated or tininseminated females.