217Plus is a methodology and a software tool that was developed by the RIAC to aid in the assessment of system reliability. It represents the next generation of the PRISM software tool initially released in 1999. The original software contained six embedded models to estimate the failure rate of various components when exposed to a specific set of stresses that are defined by the user. The 217Plus contains twelve embedded component models. Until the release of this handbook, the equations comprising the component reliability prediction models were not available in printed form. As such, a user of the old software tool could not see the exact equations that comprised the models. It is always advantageous for analysts to be able to review details of the models, so that reliability prediction results can be better interpreted and supported through mutual practitioner, management and customer understanding. The RIAC, therefore, developed and published this handbook to make available the equations and model parameters that form the basis of the 217Plus methodology.