Tostudytheexpressionofproliferatingcellnuclearantigen(PCNA)inhumangastricneoplasmanditsclinicalsignificance.TheexpressionofPCNAwassemiquantitativelyanalysedimmunohistochemically(ABC)in10gastricadenomatouspolypand94gastriccarcinomas.Results:①PCNAlabelingindex(LI)showedasignificantdifferentiationindifferentpathologicstate(Plt;0.01),②PCNALIingastriccarcinomawasindepednetofsexandage(Pgt;0.05),butcorrelatedwiththegrowingmannerofthetumor,tumordifferentiation,serosalinfiltration,nodalmetastasisandclinicalstages(Plt;0.05),③ThecorrelationwasfoundbetweenPCNALIandprognosisofgastriccarcinoma(Plt;0.05).AmoderategradeofPCNAexpressiongenerallyhadabetterprognosis.Conclusions:TheseresultssuggestthatPCNALIisafairlygoodindextoindicatebiologicbehaviorandprognosisingastriccarcinoma.