Should product architectures be considered inputs to – or outputs from – new product development (NPD)? Whereas the mirroring hypothesis suggests the former, NPD stage models suggests the latter. Elaborating on these conflicting propositions, this paper analyses the relationships between product architectures and development processes in NPD projects. The analysis demonstrates how project managers use product architectures to interpret their tasks and devise appropriate responses to perceived challenges. Thus, architectures provide useful linkages between knowledge development and organisational change in R&D organisations.