This International Standard aims to: " describe the requirements to apply when reliability block diagrams (RBD) are used in dependability analysis; " describe the procedures for modelling the dependability of a system with reliability block diagrams; " explain how to use RBDs for qualitative and quantitative analysis; " describe the procedures for using the RBD model to calculate availability, failure frequency and reliability measures for different type of systems with constant probabilities, non-repaired blocks or repaired blocks; " propose some theoretical elements to perform the calculations; " explain the relationships with fault tree analysis (IEC 61025) and Markov techniques (IEC 61165).