There is concern about poor take-up of the Medicare Part D Low-Income Subsidy (LIS), but uncertainty in published estimates. The Medicare Current Beneficiary Survey (MCBS), which contains Medicare LIS enrollment records and extensive survey data on individual beneficiary characteristics, would appear an ideal resource for evaluating LIS take-up. However, use of the MCBS to identify eligible beneficiaries is limited due to underreporting of income and lack of asset information in the published MCBS releases. We evaluate LIS eligibility and participation by enhancing the reliability of MCBS financial information using unpublished survey data on income and assets together with an income imputation procedure.