Rubus idaeus cultivars Cuthbert, Glen Isla, Latham, Newburgh and Viking, R. occidentalis (black raspberry) cultivars Cumberland, Munger and Plum Farmer and several blackberries, blackberry X raspberry hybrids and Rubus species appeared immune to graft inoculation with the virus (RVCV). Some infectible plants occurred in self progenies of Cuthbert and Latham, and some immune plants occurred in self progenies of infectible R. idaeus cv. Malling Delight. A high proportion of immune segregates was obtained in crosses involving Cuthbert, Viking, Cumberland and Malling Delight, from which it is concluded that breeding for immunity to RVCV is feasible. The continuous distribution of symptoms in these segregates, together with the results obtained from selfing, indicated that immunity was not conferred by a single major gene.