The radioprotective effects of hesperidin (HES), a flavonone glucoside, were investigated by using the micronucleus test for anticlastogenic and cell proliferation activity. A single intraperitoneal (ip) administration of hesperidin at doses of 10 mg kg(-1), 20 mg kg(-1), 40 mg kg(-1), 80 mg kg(-1) and 160 mg kg(-1) 45 min prior to gamma irradiation (2 Gy) reduced the frequencies of micronuleated polychromatic erythrocytes (MnPCEs). All five doses of HES significantly reduced the frequencies of MnPCEs and increased PCE/PCE+NCE ratio in mice bone marrow compared with non-drug-treated irradiated control (p<0.0001). There was a drug dose-response effect of HES in reducing MnPCE and increasing the PCE/PCE+NCE ratio in bone marrow cells. The maximum reduction in MnPCE was observed in mice treated with HES at a dose of 80 mg kg(-1). The total MnPCE values were 2.85 fold less in the 80 mg kg(-1) HES group after being exposed to 2 Gy of gamma-rays than those in the respective irradiated control. Our study demonstrates that hesperidin has powerful protective effects on the radiation-induced DNA damage and on the decline in cell proliferation in mouse bone marrow.