The feeding period of the grain aphid, Sitobion avenae, an important vector of barley yellow dwarf virus (BYDV), was studied in six varieties of spring barley (Hordeum vulgare L.) in an attempt to explain the resistance mechanisms in some barley varieties to BYDV. There was no significant difference in aphid feeding period between the resistant and susceptible varieties. The mechanisms underlying BYDV resistance do not seem to involve factors related to alterations in the feeding period. Suggestions for future studies are highlighted.