Current Workflow models are mainly concerned with the automation of administrative and production busines processes. These processes coordinate well defined activities which execute in isolation, i.e.synchronize only at their start/terminate states.If these models apply efficiently for a class of applications, they show their limits when one want to model the subtlety of cooperative interactions as they occur in more creative processes, typically co-design nad co-engineering processes. In this paper, we introduce the concept of cooperative workflow, i.e. a workflow model which extends classical workflow models with capabilities to synchronize activities interacting not only when they start and they terminate, but also at any point of their execution. In the spirit of the workflow approach, modeling and enactment of cooperative workflows (must) remain simple.