In this paper, we present and discuss the notion of interorganizational synthesis. Interorganizational synthesis refers to synthesis in the relationships between all organizations involved in a collaborative project. Synthesis is critical if organizations are fully to leverage the benefits of interorganizational collaboration in complex environments. Reviewing other research in management, in areas such as culture, rationality, and language, we show that collaboration is a far more complex task than economic or contractual theories suggest. We then present ten critical building blocks that must be accounted for in the design of interorganizational relations if synthesis is to be realised. Each of these blocks is discussed and the potential risks, and management implications, are also presented.