The papers in this volume were presented at the colloquium "Reduktion in der Wissenschaft: Struktur, Beispiele, philos- ophische PrObleme", held in Bielefeld, West Germany, July 18- 21, 1983. Altogether eighteen talks were delivered at the symposium, and all appear here with the exception of Professor Ehlers' address. In addition, we are pleased to be able to include three papers by invited participants (Kamiah, Ludwig, Scheibe) who were unable to attend the meeting. The meeting itself brought together a sizeable group of logicians, philosophers and working scientists to discuss and debate the theme of reduction, one that occupies a central place in contemporary philosophy of science. The participants and contributors succeeded in opening up new directions in reduction studies and presenting fresh case studies of re- duction from many different areas of scientific practice. Their efforts will greatly enhance our understanding of reduction and, consequently, our grasp of the complex process of scien- tific change and the unity and growth of scientific knowledge.