Book excerpt: The international symposium "Fundamentals of Biocatalysis in Non-Conventional Media" was organized under auspices of the working party Applied Biocatalysis of the European Federation of Biotechnology. Among the topics discussed at the symposium were physical-chemical aspects such as pH, water-activity, viscosity, dielectric constants, polarity etc. in relation to biocatalysis in non-conventional media. New measuring techniques were introduced. For people working in the field of biocatalysis in non-conventional media this book will give an excellent overview of the gain in understanding over the last five years of the fundamental aspects of biocatalysis in non-conventional media.