The 1981Cargese Summer Institute on Fundamental Interactions was organized by the Universite Pierre et Marie Curie, Paris (M. LEVY and J.-L. BASDEVANT), CERN (M. JACOB), the Universite Catholique de Louvain (D. SPEISER and J. WEYERS), and the Katholieke Universiteit te Leuven (R. GASTMANS), which, like in 1975, 1977 and 1979, had joined their efforts and worked in common. It was the 22nd Summer Institute held at Cargese and the 6th one organized by the two institutes of theoretical physics at Leuven and Louvain-la-Neuve. This time, while the last school was dominated by the impres- sive advances which were made in the field of perturbative quantum chromodynamics and its applications to high energy phenomena invol- ving strongly interacting particles, the 1981 school clearly reflected a period of transition, where the new insights gained by experiment and theory are digested and put in order. Place of pride among the experiments belonged this time to DESY. On the theore- tical side the reader will find a more thorough interpretation and understanding of the experiments as well as approaches to new theories. Finally several talks were devoted to experiments of the future. We owe many thanks to all those who have made this Summer Institute possible! Thanks are due to the Scientific Committee of NATO and its President for a generous grant and especially to the head of the Advanced Study Institute Program, Dr. R. Chabbal and his collabora- tors for their constant help and encouragements.