Abstract: Laminin and IV type collagen are a major components of the subepithelial basement membrane (BM)，was evaluated by SP immunohisochemical staining in 85cases of transitional cell bladder carcinomas.The results showed that there is a significance correlation between histlologic stage and BM staining(P<0.01),tumors with intact BM have a lower stage than tumors with patchy or absent BM;Whereas no correlation was found with tumors grade.It can be concluded that BM is a block of preventing tumor invension as well as the exoression of IV type collagen and laminin are helpful for correct staging and early identifing microinvasion of transitional cell carcinoma of bladder.