Lethal necrosis or systemic stem necrosis followed by death of Nicotiana benthamiana, severe leaf deformations of N. tabacum cv. white burley and blister formations on N. tabacum cv. samsun NN symptoms were induced by experimental inoculations of CMV RNA preparations containing satellite RNA (sat-RNA). Inoculations of RNA preparations without sat-RNA did not induce that severe symptoms on these plants, only late mild mosaic was observed. It is suggested that sat-RNA of CMV isolate has a certain role for enhancing severity of symptoms in tobacco plants. Local and systemic lethal necrosis of N. benthamiana is due to sat-RNA present with genome of CMV isolate. It is the first report of lethal necrosis induced in N. benthamiana by CMV satellite.