There are almost one million seniors in Massachusetts and while most enjoy broad coverage and protection against the cost of many health care services through Medicare, they may also face significant gaps, finding themselves responsible for substantial deductibles, coinsurance and copayments. This report, prepared by Nancy Turnbull and Katherine Heflin of Harvard T.H. Chan School of Public Health, reviews the many private and public coverage options available to seniors to supplement Medicare coverage. Using publicly available data from state and federal sources, this report examines recent trends and issues in private health insurance coverage and public programs to support payment of out-of-pocket costs for Medicare beneficiaries in Massachusetts.