The aim of this volume is to provide a survey of the latest theoretical developments and results of the structuralist program in the philosophy of science. Since the appearance of An Architectonic for Science, (a compendium on structuralism by Balzer, Moulines and Sneed) in 1987, a considerable number of contributions to the program, both on general topics and on reconstructions of particular theories, have been published. However, they appeared scattered throughout many different journals, countries, and languages. For the general public interested in philosophy of science, no overview about the state of the art was available. So, the idea occurred to the editors of this volume to bring together a number of outstanding 'structuralists' and ask them to,lay out what they have been so far doing on the research front. A conference took place in Munich in February 1994 (actually the very first conference exclusively devoted to the structuralist approach), where each contribution was amply discussed and, to some extent, 'tuned in' to the rest. The result was the present volume. All essays contained in it have been exclusively written for this project.