Background: Thyroid cancer incidence has increased almost 300% since 1975. Approximately 43,720 thyroid cancers will be diagnosed in 2023 with over 70% of them among women. Incidence is higher among White than Black women, in contrast to other cancers with higher rates among Black than White persons. Incidence rates are associated with factors related to cancer occurrence, detection, and diagnosis. The latter may be particularly true for thyroid cancer which typically is not aggressive or symptomatic during early stages and therefore often detected incidentally. These factors may differ between military and general populations and may vary by race. A previous study found higher papillary thyroid cancer incidence in active-duty servicemembers than the general population with larger differences among Black than White individuals. To further assess factors related to incidence differences between populations, further analysis by race and tumor stage/size was desirable. We conducted analyses stratified by race and tumor stage/size as well as age and gender comparing papillary thyroid cancer incidence rates between the U.S. active-duty and general populations. 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 18–59-year-old active-duty members in ACTUR and persons in SEER diagnosed with invasive papillary thyroid cancer. Active-duty population counts were sourced from the Defense Manpower Data Center. General population counts were sourced from SEER. Age-adjusted rates per 100,000, incidence rate ratios (IRR), and 95% confidence intervals (95% CI) were calculated to compare incidence rates between populations by race, gender, cancer stage (local, regional), and tumor size (0-2 cm, >2 cm). Results: This study found higher age-adjusted papillary thyroid cancer incidence rates in the active-duty military than the general population for both sexes and races. Higher incidence rates in ACTUR than SEER were more obvious for Black (IRR=2.07, 95% CI=1.56-2.70) than White (IRR=1.17, 95% CI=1.07-1.26) men and for Black (IRR=2.30, 95% CI=1.91-2.71) than White (IRR=1.50, 95% CI=1.38-1.64) women. Differences by tumor stage were observed only for localized tumors, which were larger for Black men (IRR=2.80, 95% CI=1.98-3.83; IRR=1.72, 95% CI=1.55-1.90, respectively) and women (IRR=3.07, 95% CI=2.51-3.66; IRR=1.95, 95% CI=1.76-2.15, respectively). Differences existed in 0-2 cm and >2 cm tumors, but only in Black men (0-2 cm: IRR=1.84, 95% CI=1.19-2.71; >2 cm: IRR=2.10, 95% CI=1.29-3.25) and were larger for Black than White women for smaller tumors (0-2 cm) (IRR=2.22, 95% CI=1.73-2.75; IRR=1.33, 95% CI=1.19-1.48, respectively). Within each population, differences between Black and White patients were smaller among servicemembers than the general population except among 40–59-year-olds, regionally staged tumors in men, and larger tumors in women. Conclusions: Higher incidence in the military than the general population primarily in localized tumors suggests military universal healthcare may lead to earlier detection. Larger differences for Blacks than Whites suggest such impact may be larger for Black persons, who are less likely to have timely care than White persons in the US. Nevertheless, observed population differences for tumors >2cm suggest other factors may also play a role. Disclaimer: The contents of this publication are the sole responsibility of the authors and do not necessarily reflect the views, opinions, or policies of the Uniformed Services University of the Health Sciences (USUHS), the Henry M. Jackson Foundation for the Advancement of Military Medicine, Inc., the Department of Defense (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 U.S. Government.