This volume contains the proceedings of the fIrst workshop held by the Theory and Formal Methods Section ofthe Imperial College Department of Computing. It contains papers from almost every member of the Section, from our long-term academic visitors, and from those who have recently left us. The papers fall into four broad areas: * semantics * concurrency * logic * specification with some papers spanning a number of disciplines. The subject material varies from work on mathematical foundations to practical applications of this theory, expressing the Section’s commitment to both the foundations of computer science, and the application of theory to real computing problems. In preparing the workshop and these proceedings, care was taken to ensure that there were papers overviewing a field, as well as ones whose primary aim was to present new scientifIc results. This had a dual purpose: to bring our Section members up to speed in some of the areas being worked on by the Section; and to provide the reader of the proceedings not only with a good introduction to many of the specifIc areas being investigated by the Section, but also with details of some of our latest results. All the papers presented at the workshop were revised following comments made by the workshop participants, and all were subsequently reviewed by at least two people before producing the fInal versions contained in this volume.