This volume contains selected papers presented at the 12th International C- ference on Conceptual Structures, ICCS 2004, held in Huntsville Alabama, July 19โ23, 2004. The main theme of the conference, โConceptual Structures at Workโ, was chosen to express our intention of applying conceptual structures for hum- centered practical purposes. That invites us to develop not only clear conceptual theories,butalsomethodstosupporthumansintheapplicationofthesetheories in their societies. Some promising steps in this direction are being taken, but the gap between the researchers working on a highly sophisticated level on one side and the practitioners in many ?elds of applications on the other side is usually di?culttobridge.Someofushaveexperiencesinsuchpracticalcooperation,but we need more members of our community to be engaged in โreal life problemsโ. We all know that solutions of complex problems in practice require not only a well-developed formal theory, but also an understanding of the whole context of the given problems. To support our understanding we need general philo- phical methods as well as formal theories for the representation of fundamental structures in practice. We believe that our community has powerful tools and methodsforsuccessfulapplicationsinpractice,butthatwemustdevelopaforum to present our results to a broader audience. First we must understand the s- ni?cant developments in our own group, which has activities in many directions of research.