In our preliminary study to find antiviral or antitumor agents from Korean natural products, we found that the Shope fibroma virus (SFV) induced fibromas reaching maximum size at 5~6 days with spontaneous disappearance at 15~20 days after SFV intracutaneous inoculation into Korean domestic rabbits. However, the sizes of fibromas of rabbits at day 5 after virus inoculation were significantly different individually. Assuming that the variation of tumor size was due to either susceptibility or the preexisting antibodies against SFV in the Korean domestic rabbits, the rabbits were checked for the antibodies against SFV by IFAT using SFV infected RKl3 cells. The antibody positive rate of normal Korean domestic rabbits was 32.8% and the sizes of the fibromas of the positive rabbits were significantly smaller than those of negative rabbits (p<0.0001). The fibroma sizes were dependent on the antibody titers of rabbits to SFV. The sizes of fibromas after inoculation of SFV into immunized rabbits were about one tenth of those by the first inoculation into normal rabbits. This is the first report on the antibody prevalence against SFV among normal Korean domestic rabbits and it suggest the existence of a wild fibroma virus or related virus in Korea.