In August 1979 a group of 94 physicists from 60 laboratories in 21 countries met in Erice to attend the 17th Course of the International School of Subnuclear Physics. The countries represented at the School were: Argentina, Australia, Austria, Belgium, Canada, Federal Republic of Germany, France, Hungary, India, Italy, Japan, Korea, the Netherlands, Nor way, Poland, Rumania, Spain, Sweden, the United Kingdom, the United States of America, and Yugoslavia. The School was sponsored by the Italian Ministry of Public Education (MPI), the Italian Ministry of Scientific and Techno logical Research (MRST) , the Sicilian Regional Government, and the Weizman Institute of Science. In the theoretical sessions, as expected, Sidney Coleman's (liN) lectures provided a new masterpiece in his Erice series. Andre Martin lectured on the theory of new particles, R.L. Jaffe on the Bag Hodel and Francis E. Low on quark status at low energy. In the more specialized section we were able to reflect on the problem of asymptotic changes in gauge theory, troubles experienced with instantons and finally on the fate of false vacua, thanks to A. Patrascioiu, R. Petronzio, and H. Kleinert. A quite exceptional event this year was the special QCD session wId_ch I leave the reader to enjoy without further introduction.

For almost two decades, Sidney Coleman has been giving review lectures on frontier topics in theoretical high-energy physics at the International School of Subnuclear Physics held each year at Erice, Sicily. This volume is a collection of some of the best of these lectures. To this day they have few rivals for clarity of exposition and depth of insight. Although very popular when first published, many of the lectures have been difficult to obtain recently. Graduate students and professionals in high-energy physics will welcome this collection by a master of the field.

During August 1988. a group of 67 physicists from 45 laboratories in 17 countries met in Erice for the 26th Course of the International School of Subnuclear Physics. The countries represented were: Australia. Austria. Canada. China. Czechoslovakia. Denmark. France. Federal Republic of Germany. India. Italy. Poland. Portugal. Spain. Sweden. Switzerland. United Kingdom. and the United States of America. The School was sponsored by the European Physical Society (EPS). the Italian Ministry of Public Education (MPI). the Sicilian Regional Government (ERS). and the Weizmann Institute of Science. The interest in the Superworld is still very high. This is why. for the third year. the Erice School has been devoted. to a great extent. to review the many developments in Superstring. Supermembranes with their problems of quantization and compactification. All these theoretical speculations are very far from the experimental frontier. In order to keep our feet on the ground. a series of lectures was included to cover the status of CP violation. of the Heavy Leptons. together with the projects for new physics at Gran Sasso and Fermi Lab. For completeness. Julian Schwinger reviewed the great problem of Anomalies in Quantum Field Theory and Shelly Glashow gave a closing lecture on the end of Superworld. If nothing new happens. next year there will be no Superworld in Erice.

If one knows the exact properties of a vacuum, one can predict everything. This book reviews and discusses our present understanding of “nothing”. The main results from LEP, HERA and FERMILAB are presented. In addition, new projects are discussed, as well as the current status of Higgs phenomenology and the search for supersymmetry at the major laboratories.

High energy physics has witnessed a remarkable development toward the theory of everything (TOE), whose best candidate is superstring theory. This development started with supersymmetry and has now reached the point of subjecting to experiment the problem of understanding the origin of space-time. This wide spectrum of unprecedented conceptual developments has its roots in our present knowledge of the fundamental forces of nature. This volume covers the most recent advances concerning these topics, taking into account their impact on observable phenomena. In addition, it reviews the status and prospects of all known gauge forces, including the experimental results on their validity.

During July 1991. a group of 99 physicists from 57 laboratories in 27 countries met in Erice for the 29th Course of the International School of Subnuclear Physics. The countries represented were: Algeria. Argentina. Austria. Brazil. Canada. China. France. Germany. Greece. India. Ireland. Israel. Italy. New Zealand. Norway. Pakistan. Poland. Portugal. Rumania. Spain. Sweden. Switzerland. Thailand. Turkey. The Union of Soviet Socialist Republics. the United Kingdom. and the United States of America. The School was sponsored by the European Physical Society (EPS). the Italian Ministry of Education (MPI). the Italian Ministry of University and Scientific Research. the Sicilian Regional Government (ERS). and the Weizmann Institute of Science. The opening lecture of the School was given by Professor Lev Okun. A few remarks are in order. In the pre-Gorbachev era. Professor Okun's case was the most difficult: in spite of many invitations he was not allowed to come and lecture at Erice. Nowadays the hard times have nearly been forgotten. It is with pleasure that I recall here a discussion I had with my friend Lev Okun in my house during one of his rare visits to CERN. The after-dinner topic was Galileo Galilei and his great discovery; i. e . • the equality between gravitational and inertial masses - a discovery that we are celebrating now. four hundred years later. Here is a synthesis of Professor Okun's position: given a massive particle. the only quantity we should consider when talking about masses.

From 5 to 15 August 1984, a group of 79 physicists from 61 laboratories in 26 countries met in Erice for the 22nd Course of the International School of Subnuclear Physics. The countries represented were Austria, Belgium, Brazil, Bulgaria, Canada, People's Republic of China, Denmark, the Federal Republic of Germany, France, Greece, Hungary, Iran, Israel, Italy, Japan, Korea, Malaysia, Mexico, the Netherlands, Pakistan, Poland, Sweden, Switzerland, Turkey, the United Kingdom, the United States of America. The School was sponsored by the Italian Ministry of Public Education (MPI), the Italian Ministry of Scientific and Technologi cal Research (MRST), the Regional Sicilian Government (ERS), and the Weizmann Institute of Science. The programme of the School was devoted to a review of the most significant results in theoretical and experimental research work on the interactions between what we believe today are the point like constituents of the world: quarks and leptons. It should however not be forgotten that many problems are still to be understood: especially in the forefront of the correla tion between quarks and leptons. This game started in 1966 with the proposal for "leptonic quarks" and went on with "preons" and "rishons" just to quote the most famous attempts to unify these two worlds.

These proceedings cover the most recent advances in these topics keeping in mind their impact on observable phenomena. In addition they review the status and prospects of all known gauge forces, including the experimental results on their validity.

From August to September 1998, a group of 75 physicists from 52 laboratories in 15 countries met in Erice, Italy, for the 36th Course of the International School of Subnuclear Physics. This book constitutes the proceedings of that meeting. It reviews the present status of subnuclear physics and its connections with the fundamental problems of physics, such as the unification of all gauge forces.

From 31 July to 11 August 1981, a group of 108 physicists from 75 laboratories in 27 countries met in Erice for the 19th Course of the International School of Subnuclear Physics. The countries re presented were Argentina, Australia, Austria, Belgium, Brazil, Bulgaria, Canada, Denmark, the Federal Republic of Germany, Finland, France, Greece, Hungary, India, Israel, Italy, Japan, Korea, the Netherlands, Norway, Poland, Sweden, Turkey, the United Kingdom, the United States of America, Venezuela, and Yugoslavia. The School was sponsored by the Italian Ministry of Public Education (MPI), the Italian Ministry of Scientific and Technological Research (MRST) , the Regional Sicilian Government (ERS), and the Weizmann Institute of Science. The programme of the School was mainly devoted to a review of the most significant results, both in theory and experiment, obtained in the field of high-energy interactions. The outcome of the School was to present a clear picture of how far we are along the fascina ting route towards understanding the deep meaning of the natural laws of hadronic and leptonic matter -- the final goal being the unity of all forces.