Rock stress and rock damaging are some of the main obstacles encountered when designing and constructing engineering projects with rock. This book will provide a basis to interpret acoustic emission (AE) as damage processes in stressed rock, with applications to stress measurements, size effects, source mechanisms, and fracture mechanics. The nature of rock will be described as a crystalline solid with voids in the form of small cracks and pores called damage, and AE will be explained as energy released as a result of increase in damage. Basic features of an AE monitoring system will be covered, with some background on the sensor, pre-amplifier, and data acquisition. Waveform analyses will include source locations through a geometric interpretation and a numerical algorithm, which will be available through the authors’ web sites. Fault plane solutions and moment tensor analysis will be presented for a quantitative evaluation of micromechanisms of rock failure under tension and shear. Several examples of AE monitoring will include both lab and field applications ranging from element testing to hydraulic fracturing. Intended for geologists, geophysicists and mining, petroleum and civil engineers dealing with rock stress and rock damage processes.