Abstract Background: The military population may differ from the general population in factors related to the incidence of bladder and kidney cancers. However, incidence rates of these cancers have not been systematically compared between the two populations. This study compared incidence rates of bladder and kidney cancers and their trends between active-duty servicemen and men in the general U.S. population. Methods: Data were obtained from the Department of Defense’s (DoD) Automated Central Tumor Registry (ACTUR) and the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) database. Patients were active-duty servicemen in ACTUR and men in SEER who were diagnosed with malignant bladder and kidney cancers and 18-59 years at diagnosis from 1990-2013. Age-adjusted rates, incidence rate ratios (IRR), and their 95% confidence intervals (95% CI) were compared between the two populations by age, race, and cancer stage. Trends in the incidence were also compared. Results: Incidence rates were lower in ACTUR than SEER for bladder cancer overall (IRR=0.55, 95% CI=0.48-0.62) and by age, race, or tumor stage. However, for 50-59-year-old men, the rates did not differ between the populations. Trend analysis showed bladder cancer incidence decreased more in ACTUR than SEER over the study period. Kidney cancer incidence rates were marginally lower overall (IRR=0.92, 95% CI=0.84-1.00) and significantly lower for 30-49-year-old Black men in the military than the general population. For kidney cancer, the trends were similar between the two populations with increased incidence from 1999 to 2013. Conclusion: Lower bladder and kidney cancer incidence in ACTUR, notably in younger individuals, may be primarily associated with healthier status and better health care. The lack of differences in bladder or kidney cancer incidence among 50-59-year-old men between the populations might result from more cumulative military-related exposures in this age group, which effects were offset by healthier status and better medical care. Disclaimer: The contents of this publication are the sole responsibility of the authors and do not necessarily reflect the views, opinions or policies of NCI, USUHS, HJF, the DoD or the Departments of the Army, Navy or Air Force. Mention of trade names, commercial products or organizations does not imply endorsement by the US Government. Citation Format: Julie A. Bytnar, Katherine A. McGlynn, Sean Q. Kern, Craig D. Shriver, Kangmin Zhu. Incidence rates of bladder and kidney cancers among U.S. military servicemen: Comparison with the rates in the general U.S. population [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4861.