The present volume is based on the proceedings of the 9th INFN ELOISATRON Project workshop held at the Ettore Majorana Centre for Scien­ tific Culture, Erice-Trapani, Italy, in the period July 15-26, 1989. The topic of this workshop was: Higgs Particles - Physics Issues and Experimental Searches in High Energy Collisions and it was attended by over forty participants. The concept of Higgs mechanism, like most other scientific ideas, evolved over several years, with many independent and important contribu­ tions in the sixtees to which Peter Higgs has referred in his historical account in these proceedings. However, it was not until 1967, paraphra­ sing Weinberg, that