Human whole-blood was exposed to 137Cs gamma-rays or 50 keV/microm carbon ions in the presence or absence of glycine betaine, a beer component in vitro. The dicentrics of chromosome aberrations in human lymphocytes were significantly (p < 0.05) reduced by glycine betaine after irradiation with 4 Gy of either gamma-rays or carbon ions. The maximum protection by glycine betaine for gamma-rays or carbon ions was 37% and 20%, respectively. C3H/He female mice, aged 14 weeks, received an i.p. injection of glycine betaine 15 min before whole-body irradiation with gamma-rays or 50 keV/microm carbon ions. Glycine betaine significantly (p < 0.05) increased the percent survival of irradiated mice with either gamma-rays or carbon ions. In conclusion, glycine betaine is a potent protector against damages caused by low- and high-LET radiation.