Rice transitory yellowing virus was first identified in the tropics, in northern Thailand, and designated as the Thailand isolate. The bullet-shaped virus particles about 90 nm wide and about 120 nm long were observed in the inner part of the double nuclear membrane and in the cytoplasm of the phloem cells of diseased rice plants. The leafhopper vectors, Nephotettix nigropictus, N. cincticeps and N. virescens were capable of transmitting the Thailand isolate as well as the Okinawa isolate, collected in Okinawa, in a persistent manner, but the latent period of the Thailand isolate in the vectors was slightly shorter than, that of the Okinawa isolate. The symptoms induced by the Thailand isolate were somewhat more severe and appeared earlier than those induced by the Okinawa isolate. The Thailand isolate did not appear to be identical with the Okinawa isolate in virulence, suggesting the existence of different strains. The virus was first purified by the Percoll density gradient centrifugation method and the size of the particles, 95 to 120 nm wide and 120 to 180 nm long was similar to that observed in both ultrathin sections and dip preparations from diseased rice plants. However, no virus-transmitting individuals were recovered by injection of the purified virus into leafhoppers.