The population dynamics of Mediterranean fruit fly (MFF), Ceratitis capitata (Wied.) and Peach fruit fly (PFF), Bactrocera zonata (Saund.) was studied in citrus orchards at Sinuris and Ibshaway districts, Fayoum Governorate during the two successive seasons, 2002/2003 and 2003/2004. In the meantime, rates of infestation in citrus fruits varieties were estimated at different locations. During the two successive seasons, MFF population was very low compared with PFF population. Captured insects per trap per day "CTD" for MFF ranged between 0.11-0.63 fly, with mean of 0.31 fly, and between 0.01-0.64 fly, with mean of 0.19 fly, during the two successive seasons, respectively. The "CTD" of PFF ranged between 5.2-108.2 flies, with mean of 37.46 flies and between 2.93-69.64 flies, with mean of 31.26 flies, during the two successive seasons, respectively. Total percentages of infestation with MFF & PFF together were 15.86 % and 9.98 % for Navel orange, 11.06 % and 5.35 % for Baladi orangem 12.56 % and 5.89 % for Mandrin, 10.93 % and 20.47 % for Grapevine, 9.21 % and 3.33 % for Sour orange, 1.03 % and 2.65 % for Lemon, and 1.04 % for Valencia orange (1st season only), for the two seasons, respectively. Percentage of infestation with MFF were 0.35 % and 0.02 % for Navel orange, 0.83 % and 0.68 % for Baladi orange 3.79 % and 2.29 % for Mandrin, 0.88 % and 1.15 % for Grapefruit, 3.49 % and 3.33 % for Sour orange, 0.34 % and 0.72 % for Lemon, and 0.37 % for Valencia orange (1st season only), for the two seasons, respectively. Percentages of infestation with PFF were 15.51 % and 9.96 % for Navel orange, 10.23 % and 4.67 % for Baladi orange 8.77 % and 3.60 % for Mandrin, 10.05 % and 19.32 % for Grapefruit, 5.72 % and zero % for Sour orange, 0.69 % and 1.93 % for Lemon, and 0.67 % for Valenvia orange (1st season only), for the two seasons, respectively.