It gives me immense pleasure in introducing my first book named as "High- Pressure ElectroChemistry and Applications" based on my PhD works. This book explained on newly self-developed high-pressure instruments combined with available Electro- analyzers. This deals with electrochemical aspects of the development and applications of HP-EQCM. The discussion of these aspects develops through the fundamentals of electrochemical experiments (CV, EQCM) separately or simultaneously in HP-system via the interaction of electrochemical behaviors to finally include the interfacing of the high- pressure chemistry world. The final focus is investigated on the construction and applications by HP- EQCM from 14.7 (~1 atm) to 25000 PSi. I worked consistently for almost four years