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...