An Advanced Study Institute on Fast Electrical and Optical Diagnostic Principles and Techniques was held at II Ciocco, Castelvecchio Pascoli, Italy, 10-24 July 1983. This publication is the Proceedings from that Institute. The Institute was attended by ninety-seven participants representing the United States, West Germany, the United Kingdom, Switzerland, Norway, the Netherlands, Italy, and France. The objective of the Institute was to provide a broad but comprehensive presentation of the various measurement and analy sis techniques that can be employed to investigate fast physical events, nominally in the sub-microsecond regime. This requires both an understanding of the basic principles underlying the diagnostic employed and its limitations, and a knowledge of the practical techniques available to obtain reliable and repeatable data. This Institute was thus structured to begin tutorially, followed by more practical techniques, demonstrations, and discussions. The Institute was divided into the following major sections: (1) Overview of Applications and Needs; (2) Voltage and Current Measurements; (3) Data Acquisition; (4) Grounding and Shield ing; (5) Fast Photography; (6) Refractive Index Measurements; (7) X-ray Diagnostics; (8) Spectroscopy; and (9) Active Opti cal Techniques. This Proceeding has been divided into two separate volumes. Volume 1, Current and Voltage Measurements, includes Sections (1) through (4) above; Volume 2, Optical Meas urements, includes Sections (5) through (9)."