OBJECTIVES: PCSK9 inhibitors are effective in reducing low-density lipoprotein cholesterol (LDL-C) among persons with familial hypercholesterolemia or pre-existing cadiovascular disease (CVD) whose LDL-C levels remain high on maximally tolerated statin therapy. However, the expense of PCSK9 inhibitors (> $14,000/year versus < $120 for generic statins) can pose substantial burden on patients’ out-of-pocket costs and on insurers’ drug expenditures. This is of particular concern for Medicare given the high prevalence of CVD (27% ischemic heart disease) and hyperlipidemia (45%) among Medicare beneficiaries. We examined coverage and cost-sharing for PCSK9 inhibitors (alirocumab and evolocumab) in Medicare Part D plans. METHODS: Data came from the June 2016 Centers for Medicare and Medicaid Services Prescription Drug Plan Formulary, Pharmacy Network, and Pricing Information Files for Part D plans. We determined: 1) the proportion of plans providing coverage, 2) monthly and annual out-of-pocket cost, and 3) total drug cost (plans’ 30-day retail cost), averaged across 2,575 Part D plans in 50 states and the District of Columbia. We projected beneficiaries’ annual out-of-pocket costs under a standard 2016 Part D benefit with a $360 deductible and a coverage gap, where cost-sharing increased when beneficiaries’ total drug expenditures exceeded the $3310 threshold set for 2016. RESULTS: As of June 2016, alirocumab and evolocumab were covered by 87% and 42% of plans, respectively. Required mean monthly out-of-pocket costs were high for both drugs: $336 for alirocumab and $321 for evolocumab. Beneficiaries would have entered the coverage gap in March even without filling any other prescriptions, with projected annual cost-sharing of $4988 for alirocumab and $4958 for evolocumab. This represented 35% of the annual total drug costs ($14814 for alirocumab and $13596 for evolocumab). CONCLUSIONS: The substantial cost-sharing required for PCSK9 inhibitors for Medicare beneficiaries covered by Part D may adversely affect their real-world access and adherence.