The nature of cell line, which derived from hemocytes of Chilo suppressalis larvae and persistently infected with CIV (Mitsuhashi, 1967), was investigated. 1. The whole culture incubated for a long period showed relatively high CIV-infectivity titer which revealed the persistence of the virus in this cell line. 2. The infectivity titer in the supernatant of culture began to increase after 10 days of lag phase and reached the maximum level (2.5-3.5 in -log ID_50/0.005 ml). 3. The infectivity titer of the liquid phase (supernatant) was always high as well as the titer of the cellular fraction. 4. Since 2-4% of cells showed CIV-specific immunofluorescence by fluorescent antibody technique, it was suggested that the virus multiplication occurred in some cells, but not in remaining cells by certain inhibitory mechanisms.