This is the first monograph to consider the possibility of utilizing probability theory in all essential fields of geotechnics. It deals in detail with in situ and laboratory tests, the evaluation of soil physical characteristics, the preparatory phase and the individual problems of design, including load bearing capacity, prediction of settlements, dimensioning of slopes and retaining walls, and quality control of earthworks.Numerous possibilities for, and examples of, the parallel utilization of deterministic and stochastic methods are given in the book, creating a connection between conventional and new, modern methodologies. It demonstrates by examples that the only possibility of meeting technical and economic requirements simultaneously is by using the methods of probability theory.The book also gives an account of new geotechnical and mathematical results of the author (post-evaluation of settlements and tilts, plotting of statistical bore profiles, elimination of the asymmetry of distribution by transformation, etc.). The book enables practitioners and to acquire new, modern design methods and research to develop methods. It will also be useful for undergraduate and postgraduate training.