etroviral vectors were used to introduce p53 gene. TNF-a gene orTNF-a/IL-6 genes into hnman bladder cancer cells ( E-J. BIU-87 ) . Success-ful gene integration and expression were determined by Northern hybridization.Different levels of TNFa activity of the cultnre supernatant of the cellstransduced with TNFa gene were detected by L929 bioassay.The growth rateof the tumor cells was not significantly suppressed by TNFa gene transfer,but tumor formation in BALB/c nude mice was obviously delayed, in whichthe effects revealed no difference between TNFa producers and TNFa/IL-6producers. No tumors was found in BALB/c nude mtce 9 weeks afterp53 gene-transduced cell inoculations. Expression of H-ras mRNA of the tu-mor cells transduced with p53 gene was significantly lower than the controls.