Blackgrarn mottle virus isolated from naturally infected mungbean, blackgram, and soybean plants in Thailand infected plants in the families Aizoaceae, Amaranthaceae, Chenopodiaceae, Leguminosae, Pedaliaceae and Solanaceae. The virus was transmitted by the beetles, Monolepta signata Oliv., and by mechanical inoculations in the laboratory. The properties of the virus in plant sap are a dilution end point of 10^-9-10^-10, a thermal inactivation point of 85-90°C for 10 min, and a longevity in vitro of 6-9 weeks at 20°C. Purified virus preparations had an ultraviolet light absorption spectrum typical of nucleoprotein components with a A₂₆₀/A₂₈₀ value of about 1.55. Purified virus preparations contained isometric particles with a diameter of about 28 nm. BLMV isolated from mungbean and soybean in Thailand showed reaction of identity in Ouchterlony double-diffusion tests using antise-serum against the BLMV previously reported from India, but did not react with antisera against some other beetle-transmitted viruses.