Background: This administrative claims analysis evaluated the impact of a health plan–sponsored Emergency Room Utilization Management Initiative (ERUMI), which combined increased patient copays for ED visits with educational outreach to reduce inappropriate ED use and encourage use of retail health clinics (RHCs) and other alternative treatment sites among a commercially insured population. Methods: Emergency department (ED) utilization rates for select acute but nonurgent conditions that could be treated appropriately in an RHC were compared for members of an employer group with (intervention group) and without (comparators) ERUMI. Utilization was compared for baseline period (January–June 2009) and ERUMI implementation period (January–June 2010). Results: A total of 56,896 members (14,224 intervention, 42,672 matched comparators) were included. ED utilization for conditions that could be treated appropriately by RHCs decreased by 10.39 visits/1000 members in the intervention group versus 6.29 visits in comparators. RHC visits rose for both the groups, with a greater increase in the intervention group (22.61 visits/1000 members, Pqqqlt;0.001) versus comparison (1.64/1000, P=0.064). After ERUMI implementation, intervention group members were nearly 5 times more likely than comparators to choose RHCs over ED for nonurgent care. Conclusions: The health plan–sponsored ERUMI program, consisting of both financial and educational components, decreased nonurgent ED utilization while increasing the use of alternative treatment sites.