To assess bladder cancer incidence in first-degree relatives of affected probands, bladder cancer patients and matched control probands provided general demographic and smoking information on their first-degree relatives. Bladder cancer incidence was established through information from the New York State Tumor Registry. The risk ratio for relatives of case probands versus relatives of control probands was 1.9; for relatives who smoked, the risk ratio was 2.1, while for nonsmoking relatives, the risk ratio was 1.8. Results from a proportional hazards regression analysis agreed with those above. These results indicate a familial component that is independent of smoking.