It depends. Residents of the U.S., including citizens and permanent residents, are eligible for premium-free Medicare Part A if they have worked at least 40 quarters (10 years) in jobs where they or their spouses paid Medicare payroll taxes and are at least 65 years old. Legal immigrants who are age 65 or older who do not have this work history can purchase Medicare Part A after residing legally in the U.S. for five years continuously. Legal immigrants (non-citizen permanent residents) under age 65 with disabilities may also qualify for Medicare, but typically first must meet the same eligibility requirements for SSDI (disability benefits) that apply to citizens, which are based on work history, paying Social Security taxes on income, and having enough years of Social Security taxes accumulated to equal between 20 and 40 work credits (5-10 years). New immigrants are not eligible for Medicare regardless of their age. Once immigrants meet the residency requirements, eligibility and enrollment work the same as they do for others.