Illustrates the use of probabilistic analysis in accounting for the uncertainties in the geometric as well as the material parameters in stability analysis of underground rock excavations. The relative frequency of occurrence of different failure modes and their corresponding failure probabilities are estimated. The solution hinges on a well-established deterministic vector method of analysis. As the order of uncertainty in the geometric and material parameters can be quite different, a hybrid method between the simulation and probabilistic solution proves to be simpler and efficient, and is therefore recommended.