Objective: In 2003, Oregon's Medicaid expansion program, the Oregon Health Plan (OHP), implemented premiums and copayments and eliminated outpatient behavioral health services. We ascertained whether these changes, including $50 copayments for emergency department (ED) visits, affected ED use. Methods: This study used statewide administrative data on 414,009 adult OHP enrollees to compare ED utilization rates (adjusted for patient characteristics) in 3 time periods: (1) before the cutbacks, (2) after the cutbacks, and (3) after partial restoration of benefits.