Thep53gene product has been detected frequently in various human malignancies. We have studied the expression of p53 protein in urothelial transitional cell cancers (TCCs) and examined its correlation with pathologic grade, stage(pT) and patient survival. Specimens from 69 surgically‐resected TCCs (38 cases of urinary bladder cancer, 17 cases of ureteral cancer and 14 cases of renal pelvic cancer) were examined by immunohistochemical staining, using two anti‐p53 monoclonal antibodies, PAb1801 and PAb240, and a polyclonal antibody, CM‐1. Twenty‐six TCCs (37.6%) were positively stained by at least one of the three antibodies. Statistical analysis showed a significant correlation between p53 expression and high pathologic grade (p less than 0.05, p less than 0.001) or progressive pathologic stage (p less than 0.01). In addition, in 51 of the patients who were available for follow‐up (23 cases of urinary bladder cancer, 13 cases of ureteral cancer, and 15 cases of renal pelvic cancer), the correlation between p53 protein expression and prognosis was examined. The survival of patients exhibiting positive p53 protein expression was significantly worse than those with p53‐negative tumors (p less than 0.05). These results suggest that an immunohistochemical test for p53 protein may be a useful method of evaluating the malignant potential of TCCs. Additionally, expression of p53 protein in TCCs is an indicator of a poor prognosis which should be considered in drawing up treatment