The mice B lymphocyte hybridoma cells were irradiated by 60Co?-rays with doses of 1, 2, 4, 6. 8Gy. A markedly dose-relation depression in cell survival rate, cell concentration and clone-forming rate was observed. D37 value of clone-forming rate was 8.26 Gy. Dose-relation depression was also observed in total production of monoclonal antibody of clones. But production of monoclonal antibody per clone was raised with radiation doses. These results indicate that ionization radiation depresses the survival activity of hybridoma cells, but stimulates the secretion of monoclonal antibody of survival cells.