This Standard is part of a series of ECSS Standards belonging to the ECSS-Q-ST-30 “Space product assurance - Dependability??. This Standard defines the principles and requirements to be adhered to with regard to failure modes, effects (and criticality) analysis (FMEA/FMECA) implementations in all elements of space projects in order to meet the mission performance requirements as well as the dependability and safety objectives, taking into account the environmental conditions. This Standard defines requirements and procedures for performing a FMEA/FMECA. This Standard applies to all elements of space projects where FMEA/FMECA is part of the dependability programme. Complex integrated circuits, including Application Specific Integrated Circuits (ASICs) and Field Programmable Gate Arrays (FPGAs), and software are analysed using the functional approach. Software reactions to hardware failures are addressed by the Hardware-Software Interaction Analysis (HSIA). Human errors are addressed in the process FMECA. Human errors may also be considered in the performance of a functional FMEA/FMECA. The extent of the effort and the sophistication of the approach used in the FMEA/FMECA depend upon the requirements of a specific programme and should be tailored on a case by case basis. The approach is determined in accordance with the priorities and ranking afforded to the functions of a design (including operations) by risk analyses performed in accordance with ECSS-M-ST-80, beginning during the conceptual phase and repeated throughout the programme. Areas of greater risk, in accordance with the programme risk policy, should be selectively targeted for detailed analysis. This is addressed in the RAMS and risk management plans. This standard may be tailored for the specific characteristic and constrains of a space project in conformance with ECSS-S-ST-00.