Abstract: Purpose and Methods：The mutagenielty of Cyclophosphamide(CP)and Ifosfamide(IFO)was stud— led using An1es test and SOS chromotest．Results·In Ames test both CP and IFO were found negative results on strain TA100 without metabolic activation system (S9一mix)but positive in the presence of S9一mix，showing a significant dose— dfect relationship．The mutageniclty induced by both drugs were of different degree The amount of rev~'se mutation induced by IFO was Iess than that of CP at the same dose Ieve[．At 1 0O()ug／plate dose 1evel-the amount of reverse mutation induced by CP and IF0 was twelve times and five times m0re than that of the control respectively．However，negative results were observed on strain TA97、TA98 and TA102 (without or with s9 mix)for both drugs But SOS chromotest indicated that neither CP and IFO had inducti。n SOS repair system in E Coli strain PQ35、PQ37 with or without 89 mix．Conchmion：We c0nduded that the mutagenicity of CP and IF0 was resulted from base substitution induced by themselves，and CP showed stf0ngef mutagenicity than IFO． Thus protection for workers producing or operating CP and IFO against their genotoxicity was necessary．

Key words: cyclophosphamide, ifosfamide, mutagenicity, Ames test, SOS chromotest