Veterans now make up nearly two-thirds of U.S. males aged 65 and older, and thus medical research in the male geriatric population is largely concerned with veterans, whose mortality experience assumes greater importance as they age. Department of Veterans Affairs (VA) records provide an effective and efficient means of gathering information on mortality of veterans, but are useful only if they provide relatively complete ascertainment. We investigated the completeness of VA death reporting (via the Beneficiary Identification and Records Locator Subsystem [BIRLS]) in a large cohort of nearly 32,000 World War II veteran twins followed from 1946 through 1990, comparing VA and Social Security Administration (SSA) mortality ascertainment. The small number of additional deaths found using SSA records--roughly 3% of total deaths--provides evidence that VA death reporting was nearly complete. A further capture-recapture analysis, assuming independence of BIRLS and SSA mortality ascertainment, indicated that BIRLS ascertainment was 95.4% complete.