All 24 varieties of barley tested were found susceptible to both a celery-infecting strain (CAYV) and a non-celery-infecting strain (NAYV) of aster yellows virus transmitted by Macrosteles fascifrons (Stål). Percentage of infection varied among varieties and between virus strains. There was no apparent correlation between degree of susceptibility and barley type, length of incubation period in the plant, or percentage survival of insects on varieties. Symptoms were generally slower to appear for NAYV than for CAYV. Of 3080 seeds harvested from infected plants, 2697 germinated but none of the resulting plants developed aster yellows symptoms. The symptoms produced on diseased plants are discussed and illustrated.