Seven varieties of wheat belonging to the species Triticum aestivum L. and T. durum Desf. were exposed to viruliferous Macrosteles fascifrons (Stål) and found susceptible to a celery-infecting strain (CAYV) and a non-celery-infecting strain (NAYV) of aster yellows virus. The percentages of plants infected with CAYV and NAYV, respectively were: Thatcher 9 and 16; Selkirk 4 and 16; Cascade 10 and 50; Lemhi 10 and 24; Stewart 12 and 70; Ramsey 26 and 63; Pelissier 4 and 52. NAYV infected 42% of the plants tested whereas CAYV infected only 11%. Virus incubation in the plants ranged from 21 to 56 days. Symptoms included dwarfing, chlorotic blotching, chlorosis, necrosis and premature death. No heads developed on severely affected plants but small sterile heads with distorted awns developed on plants infected later. The virus strains could not be distinguished by their symptoms on wheat.