AbstractA reliability analysis methodology, GO-FLOW, is presented. Detailed explanations and two examples of GO-FLOW analysis are given.The GO-FLOW is a success-oriented system analysis technique. The modeling technique produces the GO-FLOW chart, which is composed of operators and signal lines and represents a function of the system. A signal does not represent a“change of condition”but some physical quantity or information. The intensity of a signal represents the probability of actual or potential existence of a physical quantity, the probability that some information exists, or a time interval between two successive time points.The examples of analysis show the applicability of the GO-FLOW method to a phased mission problem (a boiling water reactor emergency core cooling system) and to a time-dependent unavailability analysis (a pressurized water reactor auxiliary feedwater system).The GO-FLOW has proved to be a valuable and useful tool for system reliability analysis.