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 "the right ideas were applied to the right problem"! Higgs mechanism, i.e. spontaneous breaking of local gauge symmetries with scalar particles becoming the longitudinal degrees of freedom of {other- wise) massless vector bosons and hence making them massive, is now an integral part of the standard {Glashow-Salam Weinberg) theory of electro- weak interactions. Fortunately for us, the structure of the standard theory prevents at least one scalar field from being transformed away. This is the Higgs particle in the standard theory - whose physics and search strategies are the subject of this workshop.