The Veterans Health Administration (VHA) has historically served a disproportionately male patient population with lower income and greater rates of mental illness than non-VHA populations. The generalizability of research based on VHA enrollees is unknown because the overlap between VHA and non-VHA populations has never been empirically examined. This study used 2013 National Health Interview Survey data to examine the extent to which VHA enrollees had similar demographic and health characteristics as individuals with Medicaid, Medicare, or private insurance coverage, based on propensity score models. A majority of male VHA enrollees were similar to Medicare beneficiaries suggesting greater generalizability of VHA studies than commonly hypothesized. Overlap declined when comparing with Medicaid enrollees or privately insured individuals, suggesting more limited generalizability of VHA studies to these populations.