There are typically three types of models involved in a geotechnical analysis, i.e., the geologic model, the ground model, and the geotechnical model, each of which may be associated with uncertainty to a different extent. However, in a typical geotechnical analysis the geological uncertainty is seldom characterized and considered explicitly. In this paper, we discuss the probabilistic tools developed in the geotechnical profession for tasks such as uncertainty characterization, assessment of impact of uncertainties, uncertainty reduction, and evaluation of the value of uncertainty reduction. We postulate that the same tools may be used for a unified treatment of various types of uncertainties in a geotechnical analysis, which would necessitate the collaboration of the engineering geologists and the geotechnical engineers to comprehensively characterize these uncertainties consistently. To this end, the probabilistic tools or methods that are widely used in geotechnical engineering are examined to determine their applicability in the evaluation of geological uncertainties. Examples are provided to illustrate various concepts introduced in this paper.