Part of states' roles in administering the new health insurance marketplaces is to certify the health plans available for purchase. This analysis focuses on how state-based and state partnership marketplaces are using their flexibility in setting certification standards to shape plan design in the individual market. It focuses on three aspects of certification: provider networks; inclusion of essential community providers; and benefit substitution, which allows plans to offer benefits that differ from a state’s benchmark plan. A review of documents collected from 18 states and the District of Columbia finds that 13 states go beyond the minimum federal requirements with respect to provider network standards, four states specify additional standards for including essential community providers, and five states and Washington, D.C., bar benefit substitution. These interstate variations in plan design reflect the challenges policymakers face in balancing health care affordability, benefit coverage, and access to care through the marketplace plans.