This study was designed to assess knowledge of AIDS among health professionals in China via a cross-sectional survey. A self-administered questionnaire requesting demographic characteristics and basic AIDS knowledge was given to health professionals in 11 provinces, cities, and autonomous regions. Questionnaires were completed by 1,400 of 1,500 (93%) health professionals surveyed. The percentages of correct answers ranged from 3% to 68%. Findings included that public health workers had more knowledge than clinicians; having attended training workshops was not associated with an adequate levels of knowledge; and knowledge differed by professional level and by the geographic region in which they worked. Although most health professionals questioned knew that AIDS is caused by an infectious agents, their knowledge of transmission routes, the "window period" and the length of the incubation period is still inadequate. Thus, health professionals in China urgently need both more training and more effective training. The effectiveness of future HIV/AIDS workshops should be evaluated.