With Commonwealth Fund support, the Center for Health Care Strategies (CHCS) established a learning collaborative to help states establish accountable care organizations (ACOs) in their Medicaid programs. Over the first two years, the collaborative assisted 10 states with developing the foundational structure for their ACO programs and incorporating nonmedical health interventions. In the third year, states will receive support as they develop sustainable payment models, integrate Medicaid ACOs into managed care environments, and build the capacity for data analysis to support broader ACO development. Lessons will be disseminated to stakeholders in all states seeking to bring accountable care to vulnerable populations.