With the development of computer technology, and especially with the advance of the Internet, information systems are becoming the vehicle for an increasing range of everyday activities. Through the computer, people can trade stocks, check email, chat with friends, play games, etc. More and more untrained people have become computer users. Intelligent agent, a technique from the field of artificial intelligence (AI), is expected to assist end users cope with increasing information overload. An intelligent agent can reduce the complexity of dialogue by understanding the goals of the user and assisting him/her to interact with the system. This paper provides a review of the methodologies used in developing intelligent agent systems.