Innovative health care delivery organizations are developing programs that aim to improve quality and demonstrate reductions in unnecessary use of acute care and costs. RAND researchers sought to identify paths to sustainability for these innovative care delivery programs. Using a sample of health plans and ACOs in Massachusetts, researchers sought to identify the methods in use to reimburse new care delivery models, criteria that health plans use to determine eligibility for these models, and criteria that accountable care organizations apply for their investments in delivery innovations. Researchers identified a highly uncertain environment for the sustainability of care delivery innovations despite a high degree of interest in these programs. Dynamics in the current environment suggest that innovation will likely be concentrated in health care delivery systems that are able to manage financial risk and that have experience and capacity in delivery innovation. For providers seeking to innovate, the central challenge will be building the capacity to manage financial risk in global payment arrangements and to support improvements in care. This will be particularly challenging for smaller organizations. Payers interested in innovation should seek ways to provide support and build the capacity of smaller and less-experienced providers so that they, too, can innovate and improve how they provide care.