The level of knowledge of AIDS was assessed by six questions in a geographically stratified random sample of 2601 adults in all states and territories in Australia. Results indicated that knowledge of AIDS was incomplete and that marital status, age, personal knowledge of somebody in a risk category for infection and occupational rank were all consistently associated with degree of knowledge about AIDS. Concern about AIDS as a social issue was related to better knowledge about AIDS, and personal concern was related to lower levels of knowledge. Sources of knowledge also discriminated degree of accurate information. These data suggest the need for more specific targeting of particular groups and an emphasis on personaly-sourced AIDS information where possible.