To clarify the clinical significance of alterations of Ha-ras, p53 and RB gene as well as infection with HPV16,18 in human bladder cancer, we examined the state of Ha-ras, p53 and RB genes, sequences of HPV16/18, and their association with clinicopathological parameters in 39 cases of bladder cancer and 7 cases of normal tissue, using nonisotopic PCR-SSCP and dot blot. The overall incidences of Ha-ras, p53 and RB gene mutation and HPV infection in tumor were 61.5% ,36% ,30.8% and 15.4% , respectively. The HPV positive rate was negatively correlated with clinical stage and pathological classification. Rather, the mutations of Ha-ras and p53 gene were positively correlated with the above clinical parameters. The incidence of Ha-ras gene mutation in recurring tumors was significantly higher than that in primary ones. A negative correlation between HPV infection and p53 mutation was also found. The results suggest that the above molecular events and their interaction play important roles in the development of bladder cancer, and that they wonld be of practical assistance in the prognosis and monitoring of bladder cancer.