It is common practice to publish conference papers in books or monograph series. This gives some advantage to those who did not have the opportunity to attend the meetings, but it irritates and disappoints others who may have hoped for a set of closely related reviews. With this book we have tried to find a compromise. It presents a selection from the topics which have been discussed in a series of inter national symposia entitled "Biophysics of Cell Surface", held in 1976, 1978, 1981, 1985 and 1988 in the GDR, and subsequently published in the journal STUDIA BIOPHYSICA (volumes 56, 74, 90, 110, 1271. Nearly all the contributors to this book participated in one or more of the meetings. We hope that our choice of topics selected for this book manages to reflect the variety and interest of the broad range of subjects which fall within the scope of membrane biophysics, without taking on the randomness of a scientific car-boot sale. We would like to express our thanks to all colleagues and organ~ isations who helped to realize the conferences and particularly this book. financial support for the symposia of 1985 and 1988 was provided by the IUPAB. A number of topics, reflected in this book, resulted in internat ional cooperations, supported by various organisations. We are especially grateful for the support of UNESCO research project on biophysicS in this respect. The European Bureau (ROSTE) of UNESCO supported the editorial work of this book.