The objective of the study was to measure the level of HIV/AIDS related anxiety among health care workers and identify its determinants. Data were obtained by means of a mailed, anonymous, self-administered questionnaire distributed to 2561 Danish medical doctors, nurses and nursing aides drawn randomly from the lists of members of the respective national associations. The data were analysed on the basis of a pre-study model including 12 variables hypothesizing a hierarchy of causal dependencies with anxiety at the top. 44% of the participants expressed HIV/AIDS related anxiety — hospital workers more than primary care workers, the older less than the younger. Anxiety was significantly associated with negative/restrictive attitudes towards HIV positives and gay men and with low levels of knowledge about HIV transmission and less education about HIV/AIDS. Negative/restrictive attitudes towards HIV positives were associated both with less knowledge regarding HIV transmission and fewer contacts with HIV positives. Similar associations were found regarding gay men. It is suggested that new kinds of training programmes be established which focus much more on attitudes and norms concerning HIV/AIDS — especially among health care workers with only occasional contact with HIV patients.