and this is reflected in the increased coverage of these topics in the book. The general form of the book remains the same. As before, a list of suggested reading, sub-divided by chapter, is provided and this has been expanded to include a greater proportion of original papers. The book is still primarily designed as an advanced undergraduate text and also to serve as an introduction for post-graduate workers entering the field of membrane research. We have taken cognizance of the comments of many reviewers, colleagues and students on the first edition and thank them for their contributions. In particular we wish to acknowledge our colleagues R. Eisenthal, G. D. Holman, D. W. Hough, and A. H. Rose. Dr. C. R.