The sixth Advanced Study Institute (ASI) on Techniques and Concepts of High Energy Physics was held at the Club St. Croix, in St. Croix, U.S. Virgin Islands. The ASI brought together a total of 70 participants, from 21 different countries. Despite logistical problems caused by hurricane Hugo, it was a very successful meeting. Hugo's destruction did little to dampen the dedication of the inspiring lecturers and the exceptional enthusiasm of the student body; nevertheless, the immense damage caused to the beautiful island was very saddening indeed. The primary support for the meeting was again provided by the Scientific Affairs Division of NATO. The ASI was cosponsored by the U.S. Department of Energy, by Fermilab, by the National Science Foundation, and by the University of Rochester. A special contribution from the Oliver S. and Jennie R. Donaldson Charitable Trust provided an important degree of flexibility, as well as support for worthy students from developing countries. As in the case of the previous ASls, the scientific program was designed for advanced graduate students and recent PhD recipients in experimental particle physics. The present volume of lectures should complement the material published in the first five ASls, and prove to be of value to a wider audience of physicists.