Triticale (Triticosecale Wittmack) is a hybrid crop developed by crossing wheat (Triticum) and rye (Secale). The associations between the concentrations of total phenols and o-dihydroxyphenols within tissues of winter triticale with their resistance to the grain aphid and bird cherry-oat aphid were studied. In the tissues of study plants, the highest amount of phenols was observed in flag leaves of transgenic plants (9.34 mg·g^-1), and the lowest in ears of wild-type control plants (1.13 mg·g^-1). Similar clear trends also were obtained for content of o-dihydroxyphenols. In general, transgenic triticale plants were more resistant to the cereal aphids than the regular ones. Aphid development time was prolonged while fecundity and intrinsic rate of natural increase (r_m) were reduced. In addition, the triticale phenolics increased the density of the cereal aphid population. The importance of the phenolic compounds in the resistance of plants (cereals) to the aphids (grain aphid) is discussed.