Field studies were carried out in Egypt during 2003/4 and 2004/5 seasons to determine the main pests of onion, their occurrence time and associated predators in addition to further studies of Thrlps !abaci Lind. on different varieties in different regions during both seasons. Results obtained showed that seven main insect pests, 6 insect predators and 4 true spider predators were present on onion plants. The population density of T tabaci was higher in 2004/5 than 2003/4 season. The investigated regions could be arranged descendingly according to the total mean numbers of thrips (nymphs and adults) per plant as, Beni-Swief (64.01), Fayoum (44.91), Quna (39.81), Aswan (23.77) and Kafr-El-Shiekh (6.93 insect/plant). Giza 20, was the highest susceptible variety for thrips infestation as resulted a general mean for both seasons, 36.7 insect/plant followed by Giza 6 (35.4) then Shndawil 1 (29.0) while Behiry var. was the least susceptible one (16.0). Thrips attack onion in nursery and perennial field and its population peaked on March. Behiery var. is highly infested by thrips under Fayoum than Kafr-EI-Shiekh conditions.