Tumor grade and stage are two of the strongest predictors for indolent versus aggressive clinical course in bladder cancer. To identify age-related trends in tumor aggressiveness the authors investigated the relationships of age with grade and stage. Pathologic specimens were obtained for 89% (527 of 590) of new bladder cancer cases among men older than 50 years of age reported to the state tumor registry in Wisconsin for 1988. Tumors were grouped as low grade (G1, G2) or high grade (G3), and as superficial (Ta) or invasive (greater than or equal to T1), according to the TNM system. This analysis included 485 transitional cell carcinomas (TCC) for which the authors determined stage-stratified and grade-stratified odds ratios for men 50 through 64 years of age and older than 65 years of age. Men older than 65 years of age with superficial TCC were more than three times as likely to have a high-grade malignancy than men 50 through 64 years of age (P = 0.01); the odds ratio was 3.44 (95% CI = 1.28, 9.26). A relationship was not apparent for invasive TCC. Age and stage were weakly associated for low-grade and high-grade TCC that may be due, in part, to the strong correlation of stage with grade as a prognostic indicator. These data suggest that men in older age groups are at increased risk for superficial bladder cancer of high grade, which portends an aggressive clinical course.