none The population densities of Dacus oleae Gmel. throughout one year were studied in three localities of Egypt, Fayoum, Tora (Cairo) and Alexandria, by the use of attracting traps baited with diammonium phosphate. The population of the fly was very low in August and mid-September, especially in Tora and Fayoum owing to the hot dry weather at this time of the year. The population in an orchard with small trees was only 1/3 that with large trees. Infestation of fruits began early in July at Alexandria and later on at Tora then Fayoum. Parasitism by Opius sp. (Braconidae) was only found at Alexandria.