The antimutangenic effect of the aqueous extract ganoderma lucidum (AEGL)were studied. The mice micronucleus test of bone marrow cell, the chromosome aberration test in mice testicle cells and the in vitro mammalian cell gene mutation test had been done. The results showed that the micronuclei frequency induced by cyclophosphamidum in mice bone marrow cell and gene forward mutation rates induced by mitomycinc in V79 cell were both inhibited significantly by the AEGL, but it had no effect on the chromosome aberration induced by cyclophosphamidum in mice testis cell. It indicated that the AEGL had preventive effects on DNA damage in body cell. Author's address: Cui Wenming, National Institute for Nutrition and Food Safety, Chinese Center for Disease Control and Prevention, Beijing 100050, PRC.