The Qualified Medicare Beneficiary (QMB) program, part of the Medicare Savings Program, provides Medicare premium and cost-sharing assistance to low-income beneficiaries but has low participation rates. We examined the potential for QMB coverage to reduce the avoidance of health care services because of cost among low-income seniors in eight states. Only one-third of eligible seniors participated. Adjusted for demographics and health status, QMB enrollees were half as likely as nonenrollees to avoid physician visits because of cost. Despite its potential to improve access to primary care, the QMB program is underused. Future policy and research efforts should address low participation rates.