The Reliability, Maintainability, and Cost Model (RMCM) described in this report is an interactive mathematical model with a built-in sensitivity analysis capability. It is a major component of the Life Cycle Cost Impact Model (LCCIM), which was developed as part of the DAIS advanced development program to be used to assess the potential impacts of the DAIS concept of avionics integration on system support requirements and life cycle cost (LCC). This guide for RMCM users contains all information needed for users to interact with the RMCM computer program from a computer terminal. Included are descriptions of the RMCM functions and capabilities, as well as each cost element which it covers and its associated equations; instructions for preparing input data files; a description of the input data format for the cost model data bank; an explanation of the interactive procedures to be used on the computer terminal; and examples of the RMCM batch mode printed outputs. The appendices contain RMCM input cost elements and sources, specific cost element equations, and a list of acronyms. (Author/CHC)