The focus of traditional workflow management systems is on control flow within one process definition, that describes how a single case (i.e., work-flow instance) is handled in isolation. For many applications this paradigm is inadequate. Interaction between cases is at least as important. This paper introduces and advocates the use of interacting proclets, i.e., light-weight workflow processes. By promoting interactions to first-class citizens, it is possible to model complex workflows in a more natural manner, with improved expressive power and flexibility.