The Proceedings of the Second International Symposium on Biochemistry of Exercise are centered on the effects of long lasting exercise and training. In the years following the first symposium which was held in Brussels in 1968, biochem istry of exercise has gained more importance in view of the increasing number of labora tories and scientific papers which are dealing with this field. From the topic of the first symposium - humoral modifications occurring during physical activity - our points of interest have been turned to a more limited area, namely long term exercise and training, It was important to investigate these subjects because everyone knows that in to-day's sport a good performance means hours of weekly or even daily training. Therefore, it was of considerable interest to stimulate discussions and to clarify ideas in this particular field of human activity. Our knowledge of biochemistry of exercise at the cellular level has highly progressed during the last five years. Researchers have focused their interests on the sequential uti lization of fuels, the adaptative responses of the enzyme machinery, the different types of muscle fibers. The topics of the Proceedings include: general subjects, metabolism of carbohydrates, lipids, and proteins, hormonal regulations, electrolytes, ultrastructure and fiber types of muscle, cellular enzymes. In the symposium, the current knowledge was summarized as an introductory lecture to each of these topics by prominent authors, namely: J. KEuL (Freiburg i. Br. ), M. ScHERRER (Bern), B. SAL TIN (Copenhagen), P.