An investigation was undertaken to obtain further information on aphid transmission of turnip mosaic virus (TuMV) and cucumber mosaic virus (CMV) from doubly infected turnip plants (Brassica campestris cv Yorii) to healthy ones. Both winged and wingless forms of Myzus persicae (SULZER) transmitted TuMV alone at a higher rate, but failed to transmit or seldom transmitted CMV alone. Both forms of Aphis gossypii GLOVER, showed three types transmission, TuMV alone, CMV alone and both viruses simultaneously, but they transmitted CMV alone more effectively. In the transmission test with successive transfers at 10-minute intervals, most of the M. persicae individuals transmitted TuMV alone to only the first plant of the series. And A. gossypii also commonly transmitted TuMV alone or CMV alone to the first plant only. When M. persicae and A. gossypii had fed first on infected leaves and then fed on anti-TuMV γ-globulin through a stretched parafilm membrane, the transmission of TuMV was prevented completely or decreased remarkably. And A. gossypii treated with anti-CMV γ-globulin after feeding on the infected leaves, transmitted TuMV regularly, but seldom transmitted CMV.