AbstractA culture of RYNV was obtained free from other detectable viruses by heat treatment of red raspberry cv. Malling Jewel showing veinbanding mosaic symptoms. Graft inoculated black raspberry (Rubus occidentalis) plants showed 3 kinds of ultrastructural abnormality: (1) cell wall outgrowths in many kinds of cells in the leaf blade and vascular bundles, (2) tubular structures c. 30 nm diam. and up to 1100 nm long, in groups in the cytoplasm close to the nucleus and (3) small bacilliform virus like particles c. 80-150 X 25 nm, randomly distributed in the cytoplasm of many kinds of leaf cells, but especially in the phloem. The bacilliform particles, which in some cells were in large groups associated with lightly staining amorphous material, are considered to be those of RYNV.