A fundamental concern with competitive health insurance markets is that they will not supply efficient levels of coverage for treatment of costly, chronic, and predictable illnesses, such as mental illness. Since the inception of employer-based health insurance, coverage for mental health services has been offered on a more limited basis than coverage for general medical services. While mental health advocates view insurance limits as evidence of discrimination, adverse selection and moral hazard can also explain these differences in coverage. The intent of parity regulation is to equalize private insurance coverage for mental and physical illness (an equity concern) and to eliminate wasteful forms of competition due to adverse selection (an efficiency concern). In 2001, a presidential directive requiring comprehensive parity was implemented in the Federal Employees Health Benefits (FEHB) Program. In this study, we examine how health plans responded to the parity directive. Results show that in comparison with a set of unaffected health plans, federal employee plans were significantly more likely to augment managed care through contracts with managed behavioral health "carve-out" firms after parity. This finding helps to explain the absence of an effect of the FEHB Program directive on total spending, and is relevant to the policy debate in Congress over federal parity. (Contains 7 tables.)