An anonymous postal questionnaire survey studying the knowledge, attitudes, beliefs and practices on human immunodeficiency virus (HIV) infection was conducted among all registered medical and dental practitioners in Singapore in 1996. In all, 1523 replies were received, yielding a response rate of 29.3%. The level of knowledge regarding transmission and prevention was generally good, although there were a number who believed that HIV could be transmitted by the respiratory and oral routes. However, knowledge regarding diagnosis and medical management was unsatisfactory. Although a large majority felt they had the ethical obligation to treat HIV patients, only half of them indicated their willingness to do so if they were given the choice. The majority (62.3%) supported the idea of routine preoperative HIV testing for patients, but fewer (40%) supported mandatory HIV testing for health care workers. Dentists seemed more sensitive to issues involving transmission in the workplace, and 95% of them practised universal precautions. Continuing medical education on HIV infection is required to improve and maintain the level of knowledge and competency of doctors and dentists in Singapore.