Blackgram mottle virus (BMoV) was isolated from mungbean plants showing mottling and mosaic symptoms in Indonesia. The virus was transmitted by mechanical inoculation, the bean leaf beetle, Colposcelis signata and golden green minute leaf beetle, Balisepta fulvipes and through infected mungbean seeds. Purified virus preparations contained isometric particles with a diameter of about 28 nm and had an ultraviolet light absorption spectrum typical of those of nucleoprotein components with a A₂₆₀/A₂₈₀ value of about 1.53. Indonesian and Thai BMoV showed reaction of identity in Ouchterlony double-diffusion tests using antiserum against Indonesian BMoV. Indonesian BMoV also reacted with antiserum against Indian BMoV, but did not react with antisera against some other beetle-borne viruses. Enzyme-linked immunosorbent assay (ELISA) test detected BMoV at concentrations as low as 50 ng/ml and was more sensitive than the mechanical inoculation test. Both ELISA and mechanical inoculation tests could easily detect BMoV at high concentrations from whole seeds, but at very low concentrations in seeds in which seed coats had been removed.