The fault tree analysis (FTA) is invaluable as this is the only deductive approach (i.e. top down or effect to cause approach) used to deal with safety and dependability modelling. This chapter describes its position within the probabilistic approaches in general and the Boolean family approaches in particular. It aims to model how a system is faulty (i.e. in down state) from the logic combination of the faults (i.e. down states) of its components: it is the dual approach of RBDs and both approaches are equivalent from a mathematical point of view. An FT is a directed acyclic graph drafted by using specific symbols (primary events) and logic gates (e.g. OR, AND, k out of n, NOT). The various primary events and logic gates are analysed and simple examples are provided to explain how to effectively build such models. The concept of minimal cut sets introduced in the RBD chapter is still valid with FTs and this is the basis for qualitative analysis from FT models. The success trees which describe how a system operates from the good operating states of its components are also briefly described.