Particle physicists sometimes complain that there has been ‘no exciting new development since last year's conference’. The complaint is justified only because the overall pace of discovery in this field has been so great. In the past decade the pace has been maintained with the discovery of the Z and W bosons and the establishment of three as the number of light neutrinos thus most probably fixing the number of the lepton and quark generations in the Universe.

Technical achievements have included the bringing into successful operation of LEP at CERN and the Tevatron at Fermilab and the collision of microscopically tightly focussed beams at SLAC. The detectors at these accelerators are among the most sophisticated pieces of hardware ever built. The great proton decay detectors have detected no decaying protons but have opened a new window on the Universe in neutrino astronomy.

In the 1960s and much of the 1970s particle physics was primarily concerned with getting the data on which QCD and Electroweak Unification have been built. Our understanding of the fundamental structure of matter has been transformed by these achievements. Current and future work is focussed on very fundamental questions which were not even crystallised in the earlier era. There remain many challenging problems: