Rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV) were isolated from rice plant infected with a Philippines isolate of tungro. RTBV was transmitted alone or together with RTSV by the leafhopper Nephotettix virescens from rice plants infected with both RTBV and RTSV, but not from plants with RTBV alone, while RTSV was transmitted alone. RTBV transmission by the leafhopper also occurred when the leafhoppers were previously fed on RTSV diseased plants. The minimum acquisition access period of RTSV and hypothetical “helper factor” for RTBV transmission by the leafhopper was 10min, and RTBV was acquired in a 30min access. The “helper factor” was retained for 7 days by the leafhopper, whereas RTSV was retained for 2 days. The “helper factor” was not retained in the leafhopper after the moulting.