Despite imminent expansion of Medicaid to low-income adults, the effects of expanding coverage are unclear. Oregon’s 2008 Medicaid expansion using lottery drawings from a waiting list provides an opportunity to evaluate the effects of Medicaid using random assignment. Approximately two years after the lottery, we collected data from 6,387 adults randomly selected to be able to apply for Medicaid coverage and 5,842 not selected. Measures included blood pressure, cholesterol and glycosylated hemoglobin; a depression screen; medication catalogs; and self-reported diagnoses, health, health care utilization and out-of-pocket spending. We use the lottery’s random assignment to calculate the effect of Medicaid coverage.We found no statistically significant effect of Medicaid on the prevalence, diagnosis, or medication of hypertension or high cholesterol. Medicaid coverage significantly increased the diagnosis of diabetes and use of diabetes medication, but we observed no significant effect on average glycosylated hemoglobin levels nor on the percent with levels >6.5%. Medicaid coverage decreased the probability of screening positive for depression (-9.15 percentage points; 95% CI: -16.70 to -1.60; P=0.018), increased use of preventive services, and almost eliminated catastrophic out-of-pocket medical expenditures. Thus, evidence using a randomized controlled design showed that Medicaid coverage generated no statistically significant improvements in measured physical health outcomes in the first two years, but did generate increased health care use, higher rates of diabetes detection and management, lower rates of depression, and lower financial strain.