Cystectomy specimens of 118 transitional cell carcinomas of the bladder were analyzed by step-sectioning. The carcinoma in situ and dysplasia adjacent to and remote from the visible bladder cancer were correlated with the tumor configuration on cystoscopy, and grade and stage of the disease. Results showed that a combination of papillary and nodular carcinomas in a single bladder was associated with a high incidence of mucosal involvement. Moreover, more than 50 per cent of all grade 3 carcinomas were associated with carcinoma in situ and dysplasia adjacent to and remote from the visible tumors. Carcinoma in situ and dysplasia were not related to the stage of disease. For management of bladder cancer, it appears important to assess the gross configuration of tumors by cystophotography and to determine the grade of tumors by biopsy, because mucosal involvement was found to be correlated closely with the tumor configuration and grade 3 disease.