Abstract Not all health insurance is created equal. Medicaid typically provides coverage with little or no patient cost-sharing, while many private non-group health insurance plans expose patients to high out-of-pocket spending. On the flip side, not all providers will accept Medicaid patients, so that access to providers may be better with private coverage. We propose to evaluate the pros and cons of Medicaid versus private coverage for low-income families using a regression discontinuity design that exploits the sharp cutoff in Medicaid eligibility in many states at 138% of the poverty level. Outcomes to be analyzed include out-of-pocket health care spending and access to care. We will also analyze the spillover effects of Medicaid versus private coverage on the use of other social welfare programs such as Food Stamps/SNAP and Supplemental Security Income (SSI). Data for the analyses will come from the Current Population Survey and the Medical Expenditure Panel Study. !