This article reports results of two studies that measured beneficiaries' knowledge of the Medicare program and related health insurance options using pre- and post-experimental designs. Knowledge was measured using multiple item indexes before and after receiving new informational materials developed by the Centers for Medicare & Medicaid Services (CMS) as part of the National Medicare Education Program (NMEP). Beneficiaries in both studies showed statistically significant gains in knowledge after receiving the new materials. Policy implications for the measurement of knowledge and creation of future versions of the materials are discussed.