During July 1990. a group of 83 physicists from 43 laboratories in 21 countries met in Erice for the 28th Course of the International School of Subnuclear Physics. The countries represented were: Algeria. Canada. Chile. China. Czechoslovakia. Denmark. France. the Federal Republic of Germany. Greece. Holland. India. Italy. Pakistan. Peru. Poland. Sweden. Switzerland. 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 new topic discussed in some detail at the School was QCD phenomenology at 200 TeV. This energy frontier represents the goal for subnuclear physics after LHC and sse. The main lecturers were T.D. Lee. L. Cifarelli. Y. Dokshitzer and A. Ringwald. There are two possibilities. one optimistic. the other pessimistic. LHC and SSC can produce remarkable discoveries. In this case. the need to go to higher energies will be obvious. In the pessimistic case. LHC and SSC will produce the strongest evidence for the validity of the Standard Model. The need for higher energies will be impelled. In neither case can we wait. If the 200 TeV frontier is to be reached within our lifetime we need to start now: thinking and preparing the tools. Theory and R&D for future detectors are the basic points of the 200 TeV frontier.

About three decades after the first experiments on deep inelastic lepton hadron scattering began to investigate the structure of hadrons, the history of this fruitful field of particle physics continues in the broad spectrum of research performed at the electron and positron proton collider HERA at DESY, where the multipurpose detectors ZEUS and H1 access ep scattering at a center of mass energy of 300 GeV and explore as yet uncharted kinematic realms of deep inelastic scattering. After the first years of data taking at HERA, each of the experiments has collected a total of roughly 40 pb 1 of e+p data, yielding sensitivity to deep inelastic e+p interactions at high four momentum transfers, Q2, where typi cal cross sections drop into the subpicobarn regime. This kinematic domain is characterized by electroweak unification, manifesting itself most markedly in the neutral and charged current cross sections, which approach an equal order of magnitude as Q2 rises above the square of the W and Z masses. Consequently, HERA allows, for the first time, studies of both types of pro cesses simultaneously with the same initial state conditions and in the same detector, and thus we can investigate the interplay of electroweak and strong forces governing the respective cross sections.