The present manual contains a collection of laboratory instructions used during an international training course on membrane biophysics which was held at Homburg in the fall of 1966. The selection of the topics dealt with in the various chapters depended on the scientific interest of the available teachers and on the availability of the necessary equipment in our laboratories. Thus, the material included in this volume does not add up to a systematic course in membrane biophysics. Instead it represents a more fortuitous collection of laboratory problems. In addition, some authors place more emphasis on teaching the more technical aspects of a method whereas others are primarily concerned with the demonstra­ tion of a significant biological phenomenon. Nevertheless, in spite of such differences of emphasis and a somewhat haphazard choice of a few methods and phenomena among many others of similar importance, it was felt that the publication of the material is desirable. Since no other laboratory manual exists so far, the present laboratory problems which were tested in actual practice may serve as a useful basis for the shaping of further training courses or for laboratory courses for graduate students in biophysics and physiology. Our thanks are due to the authors and the publisher who were patient and kind enough to cooperate with the editors during the long period between the end of the course and the appearance of the book.