1. Ring mosaic strain, a virus disease of pepper occured in nature on the variety "Sisi-togarasi" with large bright yellow mottlings on the leaves. When inoculated, the virus produced distinct rings or mottlings on the varieties "Nikko", and "Takanotume"; while "Yatuhusa", "Okinawa- ' zairai", and one or two other varieties formed primary local nectrotic spots on the inoculated leaves and the new leaves developed normally. 2. The virus affects various solanaceous plants, but is not transmissible to cucurbits. On Datura stramonium, Nicotiana glutinosa, N. repanda, and N. longiflora the virus forms primary necrotic spots on the inoculated leaves; while on two or three other solanaceous plants it forms bright yellow mottlings on the young eaves, and on Nicotiana tabacum, N. glauca, and Solanum sisymbrifolium makes distinct rings. 3. The virus retains its infectivity at 1:100.000 dilution,, but not at 1:1.000.000. The virus is inactivated when exposed to 90°C. for 10 minutes. 4. However the nature of the virus approaches to tobacco mosaic virus, it will be a strain of this virus (NICOTIANAV IRUS 1 (MAYER)A LLARD)f or the distinct ring markings on the Nicotiana tabacum, etc. and yellow mottlings on the Physalis angulata , and Solanum nigrum are different from those viroses caused by tobacco common mosaic virus.