Patient-centered medical home initiatives are central to many efforts to reform the US health care delivery system. To better understand the extent and nature of these initiatives, in 2013 we performed a nationwide cross-sectional survey of initiatives that included payment reform incentives in their models, and we compared the results to those of a similar survey we conducted in 2009. We found that the number of initiatives featuring payment reform incentives had increased from 26 in 2009 to 114 in 2013. The number of patients covered by these initiatives had increased from nearly five million to almost twenty-one million. We also found that the proportion of time-limited initiatives--those with a planned end date--was 20 percent in 2013, a decrease from 77 percent in 2009. Finally, we found that the dominant payment model for patient-centered medical homes remained fee-for-service payments augmented by per member per month payments and pay-for-performance bonuses. However, those payments and bonuses were higher in 2013 than they were in 2009, and the use of shared-savings models was greater. The patient-centered medical home model is likely to continue both to become more common and to play an important role in delivery system reform.