IEC 61078:2016 this International Standard describes: - the requirements to apply when reliability block diagrams (RBDs) are used in dependability analysis; - the procedures for modelling the dependability of a system with reliability block diagrams; - how to use RBDs for qualitative and quantitative analysis; - the procedures for using the RBD model to calculate availability, failure frequency and reliability measures for different types of systems with constant (or time dependent) probabilities of blocks success/failure, and for non-repaired blocks or repaired blocks; - some theoretical aspects and limitations in performing calculations for availability, failure frequency and reliability measures; - the relationships with fault tree analysis (see IEC 61025) and Markov techniques (see IEC 61165). This third edition cancels and replaces the second edition published in 2006. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: - the structure of the document has been entirely reconsidered, the title modified and the content extended and improved to provide more information about availability, reliability and failure frequency calculations; - Clause 3 has been extended and clauses have been introduced to describe the electrical analogy, the "non-coherent" RBDs and the "dynamic" RBDs; - Annex B about Boolean algebra methods has been extended; - Annex C (Calculations of time dependent probabilities), Annex D (Importance factors), Annex E (RBD driven Petri net models) and Annex F (Numerical examples and curves) have been introduced. Keywords: reliability block diagram (RBD)