Evidence has been presented that tumor suppressor genes p53 and Rb play a crucial role in the development of both human prostate and bladder cancer. Patients with either cancer are at an increased risk for developing the other malignancy as compared to the general population. The purpose of the present study was to investigate whether there is abnormal expression of these two suppressor proteins in both the bladder and prostate cancers of the same patient. The expression of p53 and pRb in bladder and prostate cancer specimens obtained from 15 patients having both cancers was studied using immunohistochemical staining with antibodies against these proteins. The expression of p53 and pRb in both bladder and prostate cancers of the same patient was congruent in 8 of 15 cases (53%) for p53 and 9 of 15 cases (60%) for pRb. The significance of these findings warrants further investigations.