Abstract: Objective To investigate the effects of local carbon ion irradiation on the length of survival and peripheral blood leukocyte and platelet counts of mice inoculated with pulmonary tumor cells. Methods Thirty tumor-bearing mice were randomly divided into control group (tumor-bearing but without carbon ion irradiation, n=10), 12 Gy group (n=10) and 24 Gy group (n=10). The right hind limbs of the mice, where the tumor cells were inoculated, were irradiated with carbon-ion beams at a single dose in 12 Gy and 24 Gy groups, and those of the control group received no irradiation. The peripheral blood leukocytes and platelets of the mice in all the 3 groups were counted immediately before and 7 and 14 days after irradiation, respectively, with the survival time of the mice recorded. Results There was no significant difference in the survival time of the mice between the 3 groups. The peripheral blood leukocyte counts in all groups increased after irradiation, no significant difference was noted between the two irradiation the groups and the control group. Irradiation at 24 Gy resulted in significant increase in peripheral blood platelet count on the 14th day (P=0.032, F=4.062), but no such increment was observed in the other 2 groups or on day 7 in the 24 Gy group. Conclusion Local carbon ion irradiation may not produce significant effects on the length of survival and hemogram of the tumor-bearing mice.