The Centers for Medicaid and Medicare Services (CMS) manage and monitor eligibility for the federally funded Medicaid and Medicare programs. We recently found their data on Medicaid and Medicare enrollment, use and payments very valuable in preparing a proposal to study senior's use of in-home vs. residential services. Most data is current through 2004. Medicaid Statistical Information System (MSIS data) is available in .pdf summary form or you can download Excel files directly by clicking on the zip versions. There are state-by-state comparisions of eligibility, beneficiaries, vendor payments and managed care. Because each table is presented in raw numbers, researchers may want to blend the Excel files with other sources of data (such as census data) to determine use levels within given communities. Medicaid Analytic eXtract (MAX) allows you to actually search and summarize data yourself (although limited choice options are available). It is based on the same set of data as MSIS but is compiled annually rather than quarterly so lags a couple of years behind. There is generally more detail; for example, I ran a list of the U.S. top 10 drug groups ranked by total reimbursement (anti-psychotics are ranked highest in almost every state including Minnesota).