This study was performed to investigate the effects of Aloe vera administration(500mg/kg. B.W., s.i.d., P.O.) on hematology, blood chemical values and histopathological changes of spleen in cobalt-60 gamma Irradiated mice. 1. Total leucocyte counts of aloe administered groups were less decreased and more rapidly returned to normal level than those of control group. 2. Lymphocyte counts were rapidly decreased on the 1st day after irradiation in all experimental groups, but the counts were less decreased in aloe administered groups than those of control group. 3. Erythrocyte counts, hemoglobin values and hematocrit values of aloe administered groups were maintained within normal level, but these values showed lower values on the 14th day after irradiation in control group then returned to normal level on the 21th day after irradiation. 4. There were no differences between aloe administered groups and control group In LDH, SGOT and glucose values. 5. Histopathological changes of spleen in aloe administered groups showed less lymphocytic necrosis and depletion than those of control group.