Artificial intelligence (AI) is the part of computer science that studies themes related to human intelligence simulations in a computer. It has branches such as natural language, robotics, genetic algorithm, neural networks and expert systems. This book provides the reader with a brief on artificial intelligence and extensive knowledge on the expert systems. It starts with background about the artificial intelligence followed by the second chapter which introduces the expert systems, reasons for using the expert system, architecture, key participants in development, expert system building tool and the limitations in expert systems. The third chapter gives a detail description on the development of expert system which includes the task analysis to verify that the problem to be solved is suitable for an expert system type approach, knowledge acquisition, prototype development, verification and validation.