The relationship between component and system reliability is a key factor in the improvement of plant processes and a wide variety of models have been studied, under the general headings of “Probabilistic Methods”, “Graph Theoretical Methods” and “Simulation”. An outline review of these reliability models is given as a background to the work of the thesis and the ideas were used to steer the design of the software tool, which we have developed. The tool is generic in the sense that it can be used for any production system consisting of any number of parallel production lines, although we have considered its application in detail for one system only. In particular, we describe an application of reliability theory in the modelling of a plant process, which incorporates examples of Load-Sharing, parallel and series stages and we demonstrate how the production plannmg control is related to reliability considerations. The tool has been tested in reference to a real production system, for which Quality and Reliability features have been analysed though data collection and simulation. The production system is located in Intel’s ESSM (European Site for System Manufacturmg) plant m Ireland. The plant's products are the basic components of a Pentium II processor, based on a new technology, (known as MMX or Secc), which enables enhancements for multimedia and communication applications. We have also applied our software tool to the old production line (pre-datmg Secc Technology), both for calibration purposes and to compare the two lines Software features mclude the ability to, mvestigate line reaction to changes in quality and reliability, to pmpomt problem areas, to cost failures in reliability, to explore degraded operation, stages with poor quality/reliability can be identified and Estimate the real UPH (Units Per Hour). We present an analysis of system performance and provide recommendations for possible improvements to the system.