Ribonucleic acid associated with the viral nucleoprotein components characteristic of selected strains of tobacco streak virus was analyzed by density gradient centrifugation and by separation on polyacrylamide gels. In vitro degradation of the RNA extracted was traced to enzymatic action either during virus purification or nucleic acid extraction. When this was minimized, the results still suggested heterogeneity in middle component RNA such that middle and top nucleoprotein components have an RNA species in common. Conceivably the parallel between this property and the common biological properties of these components is significant.