Purpose - To indicate the current state of development of Worldwide Web based expert systems through the review of the literature and the presentation of case studies of Web based expert systems that have been developed. Design/methodology/approach - A review of the literature of Web based expert systems is presented to provide the background to the study. Presents three case studies that exemplify the application of artificial intelligence and expert systems technology to knowledge acquisition, knowledge validation, knowledge representation, inferencing, and explanation/justification: WITS, a Web based intelligent training and support system for small to medium-sized enterprises (SMEs); Fish-Expert, a fish disease diagnosis and treatment expert system; and Web based intelligent multimedia interview system (IMIS), an expert system designed to collect information from interviews. Findings - The results indicated the benefits and challenges associated with each of the three expert systems studied in the case studies in terns of the five major functions of such systems (knowledge acquisition, knowledge validation, knowledge representation, inferencing, and explanation/justification). Concludes that in technologies have changed the way that expert systems can be developed and distributed. Originality/value - Draws attention to the sparse nature of the literature on Web based expert systems and considers whether this a true lack of interest in the subject or simply the fact that many such systems go unreported.