The accountable care organization model is rather controversial among healthcare experts. Its proponents tout the potential savings and coordinated care that could be achieved through this model. Others, however, point out that the model is not without risks, such as the potential for anticompetitive effects as providers leverage it to concentrate market power. While experts are trying to clarify such matters, many health care executives and physician practices are deciding whether to move forward with becoming ACOs. Yet they may be unaware that the limited data suggest that most organizations will lose money in the first 3 years under the ACO model.