Professional development providers can shape how teachers understand and implement new policies. Yet little research explores how providers develop the ideas teacher encounter. We explore this by examining social capital among mathematics PD providers in a region. Using social network and interview data, we identify providers in brokerage positions and analyze their interactions. We found that broker behavior depended on organizational setting. Brokers in school districts interacted around logistical issues related to PD delivery, while brokers outside of districts interacted around substantive mathematical topics. When district brokers did access substantive information, they rarely shared it. We conclude: (1) the disconnect between accessing and sharing diminished district brokers' ability to support PD in their districts and (2) the lack of substance diminished their ability to influence ideas about mathematics.