This study's objective was to describe: (1) patterns of cancer prevalence and type, (2) patient demographics, and (3) the sources, and cost, of medical care in the military beneficiary population using the Military Health System administrative databases. Calendar year 2002 patient enrollment, inpatient and outpatient encounter, and cost data from the 50 United States were analyzed to determine beneficiary cancer prevalence, demographics, source of care, cost of care, and cancer type. A total of 355,442 military beneficiaries were identified to have a cancer diagnosis (excluding nonmelanoma skin cancers) in 2002. More than two-thirds of these beneficiaries were over the age of 65, 55% were male, and 44% lived in three geographic areas of the country. Cancer of the prostate, breast, lung, and colon were most common. Almost 90% received their care outside of military medical treatment facilities and the overall cost of their care for 2002 was over $1 billion.