The present work was carried out to study the population dynamics of the mealy plum aphid Hyalopterus pruni (Geoff.) and related parasitoids and predators on apricot trees, during the two successive seasons, 2003 and 2004, at Qalubia Gover-norate. The obtained data revealed that, the occurrence of H. pruni on apricot trees covered 5 months (from February to June). The mean total numbers of this aphid species per season were 1.78 (0.01-6.37) and 2.83 (0.00-10.01) individuals./leaf. The maximum numbers of H. pruni were recorded during the 2nd weeks of April, 2003 and 2004. No aphid individuals were observed during the period extended from July to September, in the two studied seasons. Four species of parasitoids; namely Aphidius matricariae Hal., Lysiphylbus sp. (1ry parasitoids) and 2 species of Alloxysta spp. (2ry parasitoids) were recorded during this study, attacking H. pruni. These parasitoid species were found during nearly three months of each season, in connection with the population density of the previous aphid species. The first para-sitoid was the highest in its numbers. The total numbers of predatory species per season were 407 and 1082 individuals, in the two studied seasons, 2003 and 2004, respectively. The maximum monthly occurrence of these predatory species was dur-ing April, 2003 (146 individuals) and April, 2004 (581 individuals), respectively. The predator Chrysoperla septempunctata L. had the highest percentages of occur-rence among other recorded predatory species (52.83 and 73.01%, respectively). In general, the parasitoid A. matricariae and the predator C. septempunctata, could be mass reared and released for controlling H. pruni on apricot trees with other availa-ble safe control methods developed in Integrated Pest Management (IPM) programs against this pest.