AbstractLeaf tissue from plants infected with northern cereal mosaic virus (NCMV) and wheat rosette stunt virus (WRSV) was extracted with a buffer containing a non‐ionic detergent. The extracts were tested by double immunodiffusion test for comparing the G protein antigens and by immunosorbent electron microscopy with decoration for comparing the nucleocapsid antigens. The heterologous reactions could not be distinguished from the homologous, thus indicating close relationship or identity of the two viruse