To evaluate the significance of p53 overexpression on the progression of bladder cancer, seven patients with Ta bladder cancer who eventually progressed to the invasive stage ( > or = stage T1) were immunohistochemically analyzed. The immunohistochemical study was performed using the p53 protein antibody on formalin-fixed, paraffin-embedded tissue sections from all primary and recurrent tumors. In three patients, immunoreactivity was detected only at the time of disease progression, suggesting that p53 mutation may be related to the disease. However, since no staining could not be found in stage Ta bladder cancer, the patient with a risk of progression could not be detected by this immunohistochemical study.