The expansion of Medicaid coverage under the ACA offers the potential for significant increases in health care access, use, and spending for uninsured nonelderly adults with chronic conditions. Using pooled data from the Medical Expenditure Panel Survey, we estimate the potential effects of Medicaid, controlling for individual and local community characteristics. We project significant gains in access and use, except outpatient Emergency Department use, for uninsured adults who enroll in Medicaid coverage and have chronic and mental health conditions. Annual per capita health care spending for newly insured individuals is projected to grow from $2,677 to $6,370 in 2013 dollars, while out-of-pocket spending drops by $921.