Through a combination of primary and secondary research, Expert Systems in this dissertation are examined and the impact they have had on large organisations to date. This dissertation outlines what Expert Systems are and what are the advantages in developing them for an organisation. Many analysts look upon Expert Systems in various forms. Each of these forms is analysed to give a better understanding as to what Expert Systems are. The acquisition and development of Expert Systems on especially sophisticated 'shells' which run on more specialised equipment is highlighted. This is backed-up in discussion by analysing an example of Expert Systems and how they use to work back in the early 1980's which is still very much relevant because the same objectives of Expert Systems were still in place back then. How Expert Systems work is also examined in detail, as are the components that are the core formation of each Expert System. Finally, the main reason for this dissertation, research is shown that Expert Systems offer different organisations a sustainable competitive advantage. This is shown within the framework of a ‘resource-based’ theory. The view here is to show practical insights into how firms should be able to make informed choices using Expert Systems as a class of organisational resources. Following that, a conclusion is written to outline briefly the main findings of my research highlighting what Expert Systems are, how they are developed and used and the great potential benefits they can offer an organisation.