Aim To study toxic effect of cyclophosphamide on the embryonic cerebral and skeleton development of rats.Methods The pregnant rats were randomly divided into control group and experimental group(5,10,15,20 mg?kg-1 body wt).The experimental group was given cyclophosphamide and control group was given normal saline(sc)d 8~10 after becoming pregnant,and all rats were cut open the belly under anesthesia with ether at d 20 of gestation,the effects of cyclophosphamide on the embryonic body,four limbs form,cerebral and skeleton development of rat were observed.Results The embryos of 5 mg?kg-1 group were normal;the aqueduct of midbrain and left and right lateral ventricle expanded,cerebral hemisphere,lumbar vertebrae,rib,metacarpal bone were hypoplasia of embryos of 10 mg?kg-1 group and the symptoms of 15 mg?kg-1 group were graver than those of 10 mg?kg-1 group;20 mg?kg-1 group did not form embryos.Conclusion Cyclophosphamide has significant toxic effect on the embryonic cerebral and skeleton development of rats.