The article examines the process of innovation and knowledge sharing from a perspective that focuses on the influence that local circumstances can have. In particular, it looks at the problems of knowledge sharing between groups of professionals. It presents a comparative analysis of two studies, one involving two groups of IT professionals; the other a network of healthcare professionals. The data was collected in two sets. The first set consisted of the results from two earlier, independent studies; the second was collected specifically for this article. We investigate the role played by boundary objects and brokers. Through an analysis of the interplay between boundary object and broker, we uncover the dynamics of the innovation process and show that the role played by the broker can be political. We identify two strategies that are used by brokers in the selection of a boundary object. The first is directed towards achieving a balance between the actors involved and the second is directed towards controlling their activities. We conclude by suggesting that other researchers should also consider the interplay between broker and boundary object when examining cross-boundary knowledge sharing.