The expansion of Medicaid coverage under the Affordable Care Act (ACA) offers the potential for significant increases in health care access, use and spending for non-elderly adults who are uninsured and have either chronic health conditions or mental health conditions. Using pooled data from the Medical Expenditure Panel Survey, we estimate the potential effects of Medicaid, controlling for individual and local community characteristics. In estimating the multivariate models, binary outcome variables, such as the probability of a health care visit during the year, were estimated using logit regression.  Count outcome variables, such as the number of office/outpatient visits during the year, were estimated using zero-inflated negative binomial (ZINB) models. Health expenditures overall and for different service types were estimated using two-part models where the use of any health care was estimated using logit regression, and in the second part, the level of expenditures conditional on use was estimated with Generalized Linear Models (GLM) in which we specify a Gamma regression model with a log link. We project significant gains in health care access and use for uninsured adults with chronic health conditions and mental health conditions who gain Medicaid coverage. With that increased use, annual per capita health care spending (excluding out-of-pocket spending) is projected to grow from $2,677 to $6,370 in $2013, while out-of-pocket spending by the newly-insured would drop by $921.  We would expect these gains in spending to be offset at least in part by reductions in uncompensated care and charity care.