Cymbidium mosaic virus(CyMV) was isolated from Calanthe spp. showing mosaic on the leaves, collected in Yamaguchi and Kyoto Prefectures in 1986~1993. CyMV, Cal. 90-1 isolate was transmitted by sapinoculation to 12 out of 37 species in 7 out of 9 families. Sap from diseaded Tetragonia expansa was infective to Chenopodium amaranticolor after dilution to 10-5 but not 10-6, after heating at 65℃ for 10 min but not 70℃, and after 1 month at 20℃ but not 2 months. The virus particles were flexuous rod, about 475 nm long. The virus was purified from diseased T. expansa leaves and contained a single protein species of Mr27,800. The Mr of the capsid proteins(Cal. 90-1) was similar to those of two ohter CyMV isolates(Cal. 90-4, Cal. 93-14).Cal. 90-1 and Cal. 93-14 reacted with antiserum to the Cymbidium isolate (Cy-16), suggesting that Cal. 90-1 was serologically very similar to the other two CyMV isolates. Two species of dsRNA were isolated from plants infected with Cal-1 and they were similar to those of two other CyMv isolates.