IEC 61164:2004 gives models and numerical methods for reliability growth assessments based on failure data, which were generated in a reliability improvement programme. These procedures deal with growth, estimation, confidence intervals for product reliability and goodness-of-fit tests. The main changes with respect to the previous edition are: - addition of two statistical models for reliability growth planning and tracking in the product design phase; - statistical methods for the reliability growth programme in the design phase of IEC 61014; - addition of the discrete reliability growth model for the test phase; - addition of the fixed number of faults model for the test phase, clarification of the symbols used for various models; - addition of real lif examples for most of the statistical models; - numerical correction of tables in the reliability growth test example. This publication is to be read in conjunction with IEC 61014:2003.