A virus was isolated from an Australian native legume, K. rubicunda. The virus here named Kennedya yellow mosaic virus (KYMV), is sap-transmissible to a limited number of other plant species. Purified preparations of KYMV particles contain 2 types of rounded isometric particles 28 nm in diameter. Particles of 1 type are infectious nucleoprotein with a sedimentation coefficient of 110 S and particles of the other type are non-infections protein shells with a sedimentation coefficient of 54 S. Nucleoprotein particles of KYMV contain 34% single-stranded RNA with a molar base content of guanine 15%, adenine 22%, cytosine 37% and uracil 25%. The present cryptogram of KYMV is R/1 : */34 : S/S : S/*.