One of the key goals of the Affordable Care Act (ACA) is to make health insurance coverage more affordable and consumer-friendly by managing competition among health insurers through the creation of health insurance exchanges. This paper explores state actions to encourage or require participation in exchanges, and preliminary responses from health insurers in six study states. Our central conclusion is that there will be robust competition in many states and this will lead to reasonably priced premiums, with lower premiums for unsubsidized enrollees and lower subsidy costs to the federal government. Our review of initial rate filings from three states reflects this finding.