The Medicaid expansion authorized by the Affordable Care Act (ACA) will result in significant enrollment increases for state Medicaid programs. A majority of these new enrollees will receive care through a Medicaid managed care plan. This brief describes how eight states are preparing to provide Medicaid coverage to these new enrollees and, more generally, altering their managed care programs. While some challenges were noted, state officials in each of the eight states felt their Medicaid managed care programs were well positioned to handle ACA-related Medicaid enrollees. Moreover, health plan capacity was described as sufficient, although there was some concern about provider capacity.