Ultrastructure of the two forms autogenous and anautogenous eggs of Aedes(Ochlerotatus ) caspius of Egypt are described using Scanning Electron Microscope(SEM). The eggs of the two forms are slightly boat shape with quite difference in width.Chorionic cells of the ventral surface are ultimately different in both forms in shape, widthof reticulum , number and size of tubercles. The chorionic cells of the autogenous form'segg are elongate, narrow and almost curved with unusually wide, outer reticulum contain 2- 13 large tubercles along with a few number in small size. However, the anautogenousform's egg , the chorionic cells of the ventral surface fairly distinct, very regular in outlinewith thin reticulum and usually hexagonal, each cell contain one or two large tubercles withmany small scattered peripheral tubercles. Fine structure micrographic work of eggs of theEgyptian Ae. caspius provides new morphological evidence that both autogenous andunautogenous forms are certainly different and suggests that those forms are two distinctspecies.