We analyzed the clinico-pathological features of the initial tumors in 205 patients with superficial bladder cancer, admitted to Kyoto University Hospital between 1974 and 1988, to investigate the prognostic factors for progression to the muscle invasive disease or metastasis. Of 205 patients, 35 (17%) exhibited muscular invasion alone (12 patients) and/or metastasis (23 patients). Tumor multiplicity, higher grade and positive urinary cytology were the significant risk factors for later malignant progression. Expression of A, B, H-blood group isoantigens in the bladder tumor were significantly decreased from the onset in the patients with initially T1 tumor but not in those with Ta tumor. Significant loss of expression was also found at the time of progression in the initially Ta cases. Thus, loss of A, B, H-blood group antigen expression seems to be correlated with the malignant potential of superficial bladder cancer. However, more feasible and reliable diagnostic markers such as molecular genetical and biochemical markers remain to be developed to predict the malignant potential of the superficial bladder cancer.