The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a pest that infests olive fruits. The female oviposits in large green olives and larvae hatch inside the fruit, where they feed upon the fruit tissues. Larval development is completed inside the fruit. These flies cause great damage to olive production worldwide. Traditionally, insecticides have been directed against the adult stage, but the results are not efficient. This present work is a study of embryogenesis in the olive fruit fly. The external morphology of the Bactrocera oleae Rossi (Diptera: Tephritidae) egg is described from light microscopy without dechorionation. The observations were made in vivo and were photographed. The eggshell of B. oleae contains a smooth chorion with a cup-shaped anterior pole. The average length of eggs is 0.738 +/- 0.01 mm and the average diameter is 0.21 +/- 0.06 mm. The embryonic developmental progress is described as formation of the zygote, blastoderm and gastrulation, and organogenesis. The embryogenesis is completed within 65-70 h at 25 +/- 1 degrees C under laboratory conditions. External egg morphology can be useful in estimating the age of B. oleae eggs for purposes such as introducing genes into embryos by germline transformation in future studies.