AbstractPurified preparations of the virus contained a major component (126S) which tended to aggregate, and sometimes a minor component of c.58S. The former contained 2 RNA species (mol. wt. 2.6 X 106 and 1.6 X 106) some particles containing 1 mol. of the large species and others apparently 2 of the smaller species. The particles migrated as a single component both in immunoelectrophoresis tests and when electrophoresed in polyacrylamide gels. In the latter they were retarded by an increase of gel strength slightly more than were particles of raspberry ringspot virus. Virus preparations yielded 2 polypeptides (mol. wt. 44 000 and 29 000) in a molar ratio of c. 1:1.3. In size and number of polypeptide species SLRV differs fom other nepoviruses and resembles broad bean wilt virus and comoviruses, but it did not react with antisera to 7 of these viruses.