Abstract: Objective　To study K-ras gene mutation and RasP21 pro tein expression and DNA ploidy abnormality and find their correlation with progn osis in 52 cases of urothelial tumors. Methods K-ras gene mutation w as detected by polymerse chain reaction and single-stranded comformation polymo rphism and RasP21 and DNA content using flow cytomytry and celluar immunofluosec ence technique from 52 cases of urothelial tumors. Results K-ras mut ation was oberverd in 9.6% and the positive expression rate of rasP21 protein i n 69.2% 42.3% aneuploidy and 57.7% diploidy tumors were detected.DNA ploidy a bnormality and the positive expression of rasP21 protein increased well with ris e of tumor grade and stage,but had a worse prognosis(P<0.01).Conclusi on DNA ploidy abnormality and rasP21 protein overexpression have been show n to be siginificant predictors of the prognosis of urothelial tumor.