The U.S. active-duty military population may differ from the U.S. general population in its exposure to cancer risk factors and access to medical care. Yet, it is not known if cancer incidence rates differ between these two populations. We therefore compared the incidence of four cancers common in U.S. adults (lung, colorectal, prostate, andbreast cancers) and two cancers more common in U.S. young adults (testicular and cervical cancers) in the military and general populations. Data from the Automated Central Tumor Registry (ACTUR) of the Department of Defense and the nine cancer registries of the Surveillance, Epidemiology and End Results (SEER) of the National Cancer Institute for the years 1990 to 2004 for persons with ages 20 to 59 years were analyzed. Incidence rates were significantly lower in the military population for colorectal cancer in White men, lung cancer in White and Black men and White women, and cervical cancer in Black women. In contrast, incidence rates of breast and prostate cancers were significantly higher in the military among Whites and Blacks. Incidence rates of testicular cancer did not differ between ACTUR and SEER. Although the numbers of diagnoses among military personnel were relatively small for temporal trend analysis, we found a more prominent increase in prostate cancer in ACTUR than in SEER. Overall, these results suggest that cancer patterns may differ between military and nonmilitary populations. Further studies are needed to confirm these findings and explore contributing factors.