The recent health reform law promotes access to preventive care through new insurance coverage requirements. Most private insurance plans, Medicare, and Medicaid expansion programs are required to cover US Preventive Services Task Force A- and B-rated services without cost sharing. However, because the Affordable Care Act treats newly eligible and existing Medicaid beneficiaries differently, all adult Medicaid beneficiaries within a state might not be eligible for the same preventive services. This study reviewed Medicaid programs across the country and found that most states do not cover all of these recommended services as preventive measures for adults. As a result, existing adult Medicaid beneficiaries might not have coverage of the same important preventive services that most other insured people have. In addition, aspects of how preventive services are defined in many states result in confusion about coverage parameters, potentially creating an additional access barrier for existing Medicaid beneficiaries.