A case-control study was conducted in the United States to examine the relationship between urinary bladder cancer, usual occupation and industry, and cigarette smoking. A total of 2,160 bladder cancer cases and 3,979 colon and rectum comparison cases, with complete histories of occupation and tobacco use, were included in the analysis. Ever having smoked cigarettes significantly elevated bladder cancer risk (odds ratio = 2.4). A dose-response relationship was demonstrated between bladder cancer and pack-years of smoking, usual number of cigarettes smoked per day, and number of years having smoked. This study observes greater risk of urinary bladder cancer due to cigarette smoking among Black males and females than among White males and females. A significant excess of bladder cancer was found among armed services personnel; this excess was restricted to White males when the analysis was performed separately by race. Black males with 'mechanic' as their usual occupation had a significant sevenfold excess of bladder cancer. The population attributable risks for occupation and smoking were 25 percent and 51 percent, respectively. The results demonstrate the strength of the association between cigarette smoking and bladder cancer and the need to control for smoking in occupational analyses.