AbstractElectron microscopy of ultra thin sections of leaves of symptom less ‘Himalaya Giant’ blackberry and of the virus indicator species, Rubus macraei, showing severe leaf curl symptoms following graft inoculation with scions from this blackberry material, detected highly flexuous virus-like particles with an unusual ‘beaded’ structure. Such particles were restricted to a few vascular cells and were distinct from P-protein common in some such cells. They also appear to be unlike any other structures observed in thin sections of other plant material and those of any other plant virus. The name, Hawaiian rubus leaf curl virus, is proposed because of the consistent association of these beaded particles with symptoms in the Hawaiian species R. macraei. It symptomlessly infected a wide range of Rubus species and cultivars. In a field trial of cultivars of blackberry and hybrid berry near SCRI, plants of ‘Bedford Giant’ blackberry showing diffuse chlorotic line-patterns and ringspots, contained a mechanically transmissible virus that has several properties in common with ilarviruses and in Western blots reacted very weakly with antiserum to Prune dwarf virus but not with antisera to Apple mosaic virus or to Tobacco streak virus.