In 2006, Medicare beneficiaries began receiving prescription coverage benefits through Part D of the Medicare benefit. Medicare Part D plans must provide medication therapy (MTM) services. MTM services aim to improve medication use and are targeted toward eligible beneficiaries, determined by morbidity, prescription use, and anticipated cost of prescription use. Now, 10 years after the start of Medicare Part D, several changes have been made to the program's design. This article focuses on changes related to MTM and the impact that these changes have and will continue to have on Medicare beneficiaries and medication use.