The addition of bentonite suspension to inoculum allowed the recovery of infectivity of tobacco mosaic virus (TMV) on Nicotiana glutinosa L. from the homogenates of a single aphid which had been fed on infected plants or purified TMV through a membrane. Infectivity of ribonucleic acid (TMV-RNA) acquired by aphids was not recovered in this manner. Aphids lost infectivity of acquired TMV after 3 or 4 days when they were fed on 15% sucrose in 0.02 M phosphate buffer through a membrane. A majority of the infectious TMV acquired by aphids was released into honeydew, but not through the stylet into sucrose solution or leaf disks. Since the total amount of infectivity that remained in dead aphids decreased with increasing incubating periods at room temperature, it is considered that a certain quantity of TMV acquired by aphids is inactivated in the insect bodies.