Four isolates of soybean mosaic virus (SMV) from soybeans in Thailand were identified by host range, serology, transmission and electron microscopy. The host range of the four isolates differed in reactions in Chenopodium amaranticolor, C. quinoa, Tetragonia expansa and Phaseolus vulgaris 'Top Crop'. Isolates of SMV from Thailand could be classified into two serological groups which were different from a SMV isolate from Japan. The serological relationship did not appear to be correlated with the host reactions.