For systematic understanding of papillary superficial carcinoma and nonpapillary invasive carcinoma of the bladder 90 cystectomized specimens of transitional cell carcinoma of the bladder were analyzed by step-section. From gross and microscopic observations bladder cancer was classified into 3 types: type 1--multiple papillary superficial carcinomas with or without small areas of dysplasia or carcinoma in situ, type 2--multiple coexistent papillary and nonpapillary carcinomas with widespread dysplasia and carcinoma in situ, and type 3--solitary nonpapillary invasive carcinoma without dysplasia and carcinoma in situ. Actuarial 5-year survival rates for types 1 to 3 were 97, 50 and 17 per cent, respectively. Although this classification is somewhat overlapping and there is a bias that basic data are obtained from the cystectomized specimens, we believe that such an analysis is necessary for considering the histogenesis and progression of human bladder cancer.