Two large double-stranded RNA molecules, 15 and 16 kilobases, were detected in cytoplasmic male sterile (CMS) Phaseolus vulgaris by agarose gel electrophoresis. A number of smaller RNA molecules were observed in 'Sprite', a maintainer line, and recurrent backcrossing of CMS P. vulgarisx'Sprite' resulted in a combined electrophoretic pattern of the two large and numerous small RNA molecules. The large RNA molecules were seed and pollen-transmissible, but were not transmitted by grafting. The RNAs were present in revertant and restored lines derived from CMS-Sprite and therefore were not associated with the cytoplasmic male sterile trait.