Stability of underground excavations is of great importance to an operating mine because it ensures the safety of the working people and operating equipment, and successful ore production. Due to the complex geological conditions and mine constructions, and variability and uncertainty in estimating rock mass mechanical properties, the assessment of rock mass stability for an underground mine is extremely challenging and difficult. Tackling of this difficult problem is not covered in detail in any of the textbooks currently available in the rock mechanics literature. This monograph aims to cover this gap in the rock mechanics and rock engineering field. This monograph provides detailed procedures for the stability assessment and support design for an underground mine case study. It covers the background of the mine site including the monitored deformation data, the state-of-art methodologies for the stability analysis of rock masses around underground excavations, performed laboratory tests, estimation of the rock mass properties, a brief theory and background of the 3-D Distinct Element Code (3DEC), and numerical modeling of underground rock mass stability including investigation of the effectiveness of rock supports. The monograph is an excellent reference for the senior undergraduates, graduate students, researchers and practitioners who work in the Underground Rock Mechanics and Rock Engineering area in the Mining Engineering, Civil Geotechnical Engineering and DEM (Distinct Element Method) Numerical modeling.