Lipases are a highly interesting class of enzymes, since they exhibit activity only at the waterlipid interphase. They are also of high practical relevance, since they are key enzymesin fat metabolism, and they can be utilized for various industrial applications such as detergents and chiral synthesis. Progress in both basic understanding and industrial use is hampered, however, by the lack in fundamental knowledge about lipase structure and function. As a result, the CEC has decided to support a 3 years’ program onthe structure analysis and protein engineering of lipases, in the framework of a BRIDGE program (see the following article of Dr. B. Nieuwenhuis). As a starting point, a CEC-GBF Workshop underlying this monograph was held in Braunschweig from Sept. 12-15, 1990, summarizing the present state of knowledge in this important area of biochemistry. Fortunately, researchers from most groups active in this field from around the world gathered at this workshop, as indicated in Fig. 1. As a result, the meeting permitted for an up-to-date assessment of the area, on a global scale. Since the contributions of all active participants were submitted in written form during the workshop, this monograph gives an excellent survey on the field of lipase structure, mechanism and cloning. At this point, I would like to acknowledge the invaluable contribution of several individuals who have greatly contributed to this endeavour. First, I would like to thank the two co-organizers and co-editors of this monograph, Prof. Lilia Alberghina of the Universita degli Studi di Milano and Dr. Robert Verger of the CNRS Marseille, for their most important contributions in the invitation of the specialists, the preparation and the organization of the workshop. Special thanks are due to the CEC, represented by the BRIDGE Lipase Project Leader, Dr. Benedict Nieuwenhuis, for both financial support and organizational help. The German government, through the GBF, its National Research Center for Biotechnology, has contributed strongly through financial subsidies and indirect help, mainly in organization. On a more personal note, I would like to acknowledge the assistance of Dr. Marianne Kordel in thefinal preparations of the workshop, of many students and assistants in our group, and in particular of Ms. Birgit Balster and Ms. Sylvia Lenk for taking care of the workshop secretariat and the preparation of this monograph. Finally, the experienced andskillful help of Dr. Johann Heinrich Walsdorff as the copy editor of this monograph is gratefully acknowledged.