Experiments were conducted to estimate the susceptibility of five tomato hybrids (Supper-gekal, F1Gs-12, Marwa, El-basha 1077 and Salymia 65010) to infestation with Tetranychus urticae Koch and its population fluctuation during the two successive seasons, summer 2013 and 2014, at Giza governorate. Supper-gekal and F1Gs-12 hybrids were the most highly significant susceptible to infestation. It recorded 31.16 (25.10%) & 24.61 (24.82%) and 28.10 (22.63%) & 22.09 (22.28%) moving mite stages / leaflet during 2013 and 2014 seasons, respectively, followed by moderate infestation observed on hybrids (El-basha 1077 and Marwa), being 25.20 (20.29%) & 19.80 (19.96%) for the former; 21.32 (17.17%) & 17.67 (17.82%) for the latter hybrid during the two seasons, respectively. The lowest infestation was observed on Salymia (65010) hybrid which recorded, 18.38 (14.81%) and 15.00 (15.13%) during the two successive seasons, respectively. Susceptibility of five tomato hybrids to infestation with T. urticae may be affected by plant leaf morphological and histological characteristics and its chemical contents. The number of leaf trichomes /cm² in upper and lower surfaces averaged (2606&8606), (3939&10557), (5788&9000), (7030&13870) and (10970&16818) for Supper- gekal, F1Gs-12, El-basha 1077, Marwa and Salymia 65010, respectively, the less number of trichomes the more mite infestation. Also, the mean thickness of lower epidermis was 19.61, 18.85, 27.57, 22.63 and 26.55 µm, while the upper epidermis was 25.64, 28.58, 27.77, 26.78 and 30.50 µm for the aforementioned hybrids, respectively. Positive relationship occurred between mite infestation levels and total carbohydrates in tomato leaves, while a negative relationship were found with alkaloids and total phenolic compounds, total flavonoids and total carotenes. Mite populations reached its peak in the 1^st week of October in the first season, while during the second season occurred in the 2^nd week of September and the 1^st week of October. The high population density of T. urticae found in 2013 compared with 2014 might be due to environmental conditions.