The efforts spent on many a scientific book cannot be justified, no matter how many words are said about it. The opposite is true for this book and a few brief remarks upon its publication. Within a short period of time, short even by all present standards, gel chromatography has gone through a development and experienced an accep­ tance that are unknown to any other method. From experience the new and unique separation technique is today known and liked in all laboratories that are concerned with substances of high molecular weight; in others, the technique is known from hearsay, at least. It has become evident that a comprehensive coverage of the conceptual development, the theoretical principles, and the experimental technique of the new method would be desirable. This coverage is now offered by the book of an expert. Its author has personally participated in the development from its beginning and has helped to promote it. He initiated gel chromatography of many substances, including proteins, on thin-layer plates; for lipophilic substances he has contributed considerably to the transition from water to organic solvent systems and developed theoretical concepts for a better understanding of the effects that are responsible for the separation. This book appears to me to point in new directions. The reader receives not only a clear presentation of facts but also instructions for practical applications.