The 1990 Cargese Summer Institute on ZO-Physics was organized by the Univer- site 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, since 1975, have joined their efforts and worked in common. It was the ninth Summer Institute on High Energy Physics orga- nized jointly at Cargese by these three universities. Because of the start-up of LEP in the summer of 1989, we broke with our tradition of having our Summer Institutes in the odd years. Indeed, it seemed to us that the many new data from LEP had to be presented in detail as soon as possible in order to prepare the young researchers in particle physics better for the experimental results with which they will be confronted in the coming years. The main theme of the school was therefore ZO-physics, with particular emphasis on the way the experiments at LEP are analyzed. We had one lecturer from each LEP experiment: they agreed among each other to present different topics in e+e- physics. Nevertheless, they made sure that all the major topics were discussed and that the results could be critically compared.

The 1983 Cargese Summer Institute on Particles and Fields was organized by the Universite Pierre et Marie Curie, Paris (M. LEVY and J.-L. BASDEVANT), C.E.R.N. (M. JACOB), the Universite Catholique de Louvain (D. SPEISER and J. WEYERS), and the Katholieke Universiteit Leuven (R. GASTMANS). After 1975, 1977, 1979, and 1981, it was the fifth time they joined their efforts for organizing this Summer Insti- tute. This school was characterized by simultaneous progress in the theory of elementary particles and by impressive experimental advances. On the theoretical front, one witnessed the new developments in lattice gauge theories, which explore the world of strongly interacting par- ticles in a non-perturbative way, and progress in a better understan- ding of the unity of all interactions based on supersymmetry. The experimentalists were ~roud to announce the discovery of the interme- diate vector bosons; W- and ZO, at C.E.R.N., while physicists working with e+e- colliding beams continued to probe more deeply the validity of the theoretical models of strong, weak and electromagnetic inter- actions. We owe many thanks to all those who have made this Summer Insti- tute possible! Thanks are due to the Scientific Committee of NATO and its Presi- dent for a generous grant and especially to the head of the Advanced Study Institute Program and his collaborators for their constant help and encouragement. We also thank the National Science Foundation (USA) for their financial assistance.

The 1990 Cargese Summer Institute on ZO-Physics was organized by the Univer- site 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, since 1975, have joined their efforts and worked in common. It was the ninth Summer Institute on High Energy Physics orga- nized jointly at Cargese by these three universities. Because of the start-up of LEP in the summer of 1989, we broke with our tradition of having our Summer Institutes in the odd years. Indeed, it seemed to us that the many new data from LEP had to be presented in detail as soon as possible in order to prepare the young researchers in particle physics better for the experimental results with which they will be confronted in the coming years. The main theme of the school was therefore ZO-physics, with particular emphasis on the way the experiments at LEP are analyzed. We had one lecturer from each LEP experiment: they agreed among each other to present different topics in e+e- physics. Nevertheless, they made sure that all the major topics were discussed and that the results could be critically compared.

The 1981 Cargese 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 Kotholieke Universiteit te Leuven (R. GASTMANS), which, since 1975 have joined their efforts and worked in common. It was the 24th Summer Institute held at Cargese and the 8th one organized by the two institutes of theoretical physics at Leuven and Louvain-Ia-Neuve. The 1985 school was centered around two main themes : the standard model of the fundamental interactions (and beyond) and astrophysics. The remarkable advances in the theoretical understanding and experimental confirmation of the standard model were reviewed in several lectures where the reader will find a thorough analysis of recent experiments as well as a detailed comparaison of the standard model with experiment. On a more theoretical side, supersymmetry, supergravity and strings were discussed as well. The second theme concerns astrophysics where the school was quite successful in bridging the gap between this fascinating subject and more conventional particle physics. 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 and to the "Region Corse" for a generous grant. .. We wish to thank Miss M-F. HANSELER, Mrs ALRIFRAI, Mr and Mrs ARIANO, and Mr BERNIA and all others from Paris, Leuven, Louvain-la-Neuve and especially Cargese for their collaboration.

The Summer Institute on High Energy Physics was the second of this kind organized at Louvain. Four years ago we had already decided to organize a Summer Institute. The first one was con- ceived in 1970, at Kiev, by D. Speiser, J. Weyers, and G. Zweig, and thanks to a NATO grant took place from August 20th to Septem- ber 15th 1971, at Louvain in the Groot Begijnhof. All lectures were directed toward one subject: duality. The lecturers were R. Brout (ULB - Bruxelles), D. Fairlie (University of Durham), F. Gilman (SLAC - Stanford), D. Horn (University of Tel Aviv), J. Mandula (Caltech - Pasadena), C. Michael (CERN - Geneva), J. Rosner (University of Minnesota), C. Schmidt (CERN - Geneva), J. Veneziano (The Weizmann Institute), J. Weyers (UCL - Louvain and CERN - Geneva), and G. Zweig (Caltech - Pasadena). The direc- tion was in the hands of F. Cerulus (KUL - Louvain), R. Rodenberg (Technische Hochschule, Aachen), D. Speiser (UCL - Louvain), and J. Weyers (CERN - Geneva). Unfortunately it was not possible to publish the lecture notes for that Institute. The second Summer Institute on Elementary Particle Physics took place from August 12th to August 25th 1973, again in Louvain. It was initiated in Chicago, in 1972, by F. Halzen (University of Wisconsin) and J. Weyers (UCL - Louvain and CERN - Geneva). Lecturers included R. Carlitz (University of Chicago), F. Gilman (SLAC - Stanford), F. Halzen (University of Wisconsin), D.

The 1979 Cargese Summer Institute on Quarks and Leptons was organized by the Universite Pierre et Marie Curie, Paris (M. LEVY and J.-L. BASDEVANT), CERN (M. JACOB), the Universite Catholi~ue de Louvain (D. SPEISER and J. WEYERS), and the Katholieke Universiteit te Leuven (R. GASTMANS), who, like in 1975 and 1977, had joined their efforts and worked in common. It was the 20th Summer Institute held at Cargese and the 5th one organized by the two institutes of theoretical physics at Leuven and Louvain-la- Neuve. This time, the school was dominated by the impressive advances which were made in the field of perturbative ~uantum chromodyna- mics and its applications to high energy phenomena involving strongly interacting particles. The unification of weak and electromagnetic interactions being well established, a new picture in particle physics emerges wherein a possible unification of weak, electromagnetic, and strong forces is put forward. Its conse~uences were also discussed in detail. Finally, to complete the picture of the present status of high energy physics, experi- mentalists from the major laboratories around the world reported on the latest developments in electron-positron scattering, neutrino induced reactions, and hadron collisions. 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 Scientific Affairs Division, Dr. M. DI LULLO for his constant help and encouragements.