The fifth policy brief in a Mathematica series examining the Medicaid Buy-In program uses Medicaid eligibility and claims data from eight study states to compare the demographics, health status, and Medicaid expenditures of Buy-In participants with individuals enrolled in Medicaid because they have a disability, but who are not taking part in the Buy-In program. The brief notes that on average, Buy-In participants cost Medicaid $984 per-member per-month (PMPM) in 2000, almost 40 percent lower than the cost of other Medicaid enrollees with disabilities. Buy-In participants were more likely to receive treatment for psychiatric conditions than other similar Medicaid enrollees with disabilities, and Buy-In participants with only a single psychiatric condition cost less PMPM than participants with a single nonpsychiatric condition or participants with multiple conditions.