A number of cereals and other grasses were compared as hosts for different isolates of viruses causing Agropyron mosaic (AMV), wheat streak mosaic (WSMV), barley stripe mosaic (BSMV), ryegrass mosaic (RMV) and orchard grass mosaic (OMV). Lolium multiflorum L. was susceptible to all the viruses. The four varieties of wheat tested were highly susceptible to AMV, WSMV and BSMV, but not to RMV or OMV. Clintland oats was susceptible to WSMV, RMV and OMV but not to AMV or BSMV. Lolium perenne L. and Dactylis glomerata L. were infected by RMV and OMV only, Agropyron repens L. Beauv. by AMV only, and Setaria italica L. Beauv. by BSMV only. Brant and Husky barley were slightly susceptible to AMV, but seven other varieties appeared immune. Unusual host records include the infection of Setaria lutescens (Weigel) Hubb. and one plant of Agropyron smithii Rydb. with WSMV, and the infection of Agropyron intermedium (Host) Beauv. with BSMV. A list of differential hosts is proposed.