The obtained results showed that grain aphid (Sitobion avenae Fabr.) feeding caused an increase of the total protein content and a decrease of soluble protein level in the ears of both studied winter triticale cultivars (i.e. susceptible cultivar Grado and relatively resistant - Lasko). Moreover, the content of amino acids in soluble protein increased in Grado plants infested with the aphid, and reduced - in Lasko.