e-Learning has revolutionized the way in which undergraduate medical education is delivered. One e-learning tool of note is the virtual patient (VP), a type of computer software that simulates real-life clinical scenarios, in which the learner emulates the role of health care provider to obtain the history, conduct examination, and make diagnoses and management decisions. VPs have been in use since 1993. Early designs were based on serial screen-cards of patient history, examination, investigations, diagnoses, treatment, and outcome, which the learner explored. With the development of web technology, VPs can now be accessed via the Internet and are more versatile, supporting different structural designs to suit a variety of learning objectives, and they can branch via different routes through a case. Using VPs has a number of advantages: 1) VPs improve access to learning material, 2) VPs help learners to acquire higher order cognitive skills like strategic thinking and decision making, 3) VPs provide a safe environment to practice, 4) VPs help to teach interdisciplinary care, and 5) VPs can be used instead of patients for examination. A number of well-known VP player systems are in use today: CASUS, CAMPUS, web-based Simulation of Patients, OpenLabyrinth, and vpSim. At the Chinese University of Hong Kong, we have also developed a web-based VP authoring and player system called Formative Assessment Case Studies (FACS), which is run by our Teaching and Learning Resources Centre. FACS has been integrated into Year-5 Anesthesia teaching since 2006. Three VP products have been developed: Anaesthesia FACS (six cases) that teaches preoperative assessment, Acute Pain Management FACS, and an eight-part longitudinal VP which tells the story of a patient's stay, and anesthesia care, for routine gynecological surgery. Students spend about 3 hours on each during a 2-week clinical attachment. Our VPs have been well received and have overcome problems of providing adequate clinical exposure.