1. Introduction. 2. General Characteristics of Rock Masses. Geological structure. Physical properties. Mechanical properties. 3. Site Investigations. General remarks. Cartographic measurements. Geophysical methods. Geological mapping. Exploratory excavations. 4. Determining the Properties of Rocks and Rock Masses. General remarks. Properties of rocks - laboratory tests. Properties of rock masses - field investigations. 5. Models and Geotechnical Classifications of Rock Masses. General remarks. Physical models. Mechanical models. Geotechnical classifications. 6. Distribution of Stresses in a Rock Mass. Examples of analytical solutions for the distribution of stresses and displacements. Numerical methods. Studies on the distribution of stresses and displacements by using physical models. 7. Failure of Rocks and Rock Masses. General remarks. Failure of rocks. Failure of rock masses. 8. Hydraulics of Rock Masses. General remarks. Flow of water through joints in a rock mass. Methods for modelling flow in rock masses. 9. Engineering Problems. General remarks. Stability of a dam foundation. Stability of slopes. Stability of underground structures associated with hydrotechnical projects. Stabilization of rock masses. Monitoring the behaviour of rock masses during construction and exploitation of structures founded on them. Subject Index.