The gel precipitin test and reticuloendotheliosis virus (REV) isolation were carried out with antigen of REV strain T on 309 chicken sera collected from 32 flocks in 1964-65 (group A) and on 430 chicken sera from 42 flocks in 1974-75 (group B). Positive results were obtained from 5.2% of the sera and 25.0 % of the flock of group A and 2.6% of the sera and 11.9% of the flock of group B. It was clarified that REV was present in Japan already in 1964. Antibody was positive in 32.9%, on the average, of the flocks surveyed.
In all the positive cases of the gel precipitin test, the precipitation line was completely agreeable with that of immune serum to REV strain T. These cases were also positive for the indirect fluorescent antibody technique.
