The infestation levels of bird cherry-oat aphid, Rhopalosiphum padi L. wer been studied on five wheat (Triticum aestivum) varieties viz., Giza 168, Sides 1, Gemmeiza 7, Gemmeiza 9 and Sakha 93 throughout 2005\06 and 2006\07 growing seasons at the Agricultural Research Institute, Ismailia governorate, Egypt. Recorded relative population densities of R. padi were correlated with some abiotic (temperature and relative humidity) and biotic (predators & Parasitoids) factors during both seasons. Sids 1 variety showed highest susceptibility, while Sakha 93 variety was the least susceptible one. Results showed significant differences between the five wheat varieties for R. padi population abundance (adults and nymphs) in both seasons. Presence and rates of phytochemical components in leaves of the different wheat varieties were studied.