The purpose of this book is to bring together in a single volume current knowledge and basic data on geothermal energy resources in the State of Arizona. We hope that our preliminary investigations, data compilations, and models will provide investigators with a sound scientific basis for future exploration and development work. For readers primarily interested in understanding geothermal energy, what it is, and its sources and occurrences in Arizona, we hope this volume provides helpful insights into all aspects of this most fascinating alternate energy source. Following the introductory chapter, this report is divided into major sections as follow. Ch. 2, specific area investigations; Ch. 3, thermal aspects of Arizona; Ch. 4, exploration methods. References follow each section. Basic data not in this report can be found in the original open-file reports, as referenced. (398 pages)