The strong trend in the Biological Sciences towards a quantitative characterization of processes has promoted an increased use of thermo­ dynamic reasoning. This development arises not only from the well­ known power of thermodynamics to predict the direction of chemical change, but also from the realization that knowledge of quantitative thermodynamic parameters provides a deeper understanding of many biochemical problems. The present treatise is concerned primarily with building up a reliable data base, particularly ofbiothermodynamic and related quantities, such as partial specific volumes and compressibilities, which will help scientists in basic and applied research to choose correct data in a special field that may not be their own. Most chapters reflect this emphasis on data provision. However, it was also felt that the expert user deserved information on the basic methodology of data acquisition and on the criteria of data selection. Therefore all tables are preceded by a critical evaluation of the techniques as well as a survey of the pertinent studies in the corresponding areas. The surveys are usually self-consistent and provide references to further sources of data that are important but not covered in the present volume. The reader will realize that in different chapters, different symbols have be~n used for the same properties. This unfortunate situation is particularly obvious in those chapters where partial specific or molar quantities had to be introduced; however, it also occurs in those contributions concerning phase changes of macromolecules.