The mechanism through which seminal material is transferred from the Aedes aegypti male mosquito to the female, and a detailed description of the male and female genital systems are presented. It was observed that the aedeagus of the male mosquito is placed superficially within the genital orifice of the female during copulation and is not a deep intromittent organ. Sexual union was accomplished through the junction of the everted male aedeagus and the atrial membrane of the female. Observations suggested that contractions of the male accessory gland provide the current in which sperm are carried to the copulatory bursa of the female, and that the sperm are subsequently transferred to the spermathecae. The complex stimuli necessary to initiate mating in this mosquito species are also discussed.