A population-based study was conducted to investigate about AIDS knowledge and attitudes among the general public in Tehran, Iran. Using a short questionnaire a random sample of 1172 individuals aged between 15 and 65 years were interviewed. The mean age of the respondents was 34.8 (S.D. = 12.9) years, 52% were male and mostly married (70%), and had received secondary education or above (84%). The findings indicated that the respondents had a fairly good to excellent knowledge about AIDS. The correct answers ranged from 53% to about 99%. Also the results showed that the majority of the respondents were strongly agree or agree with the statement that people with AIDS should have social right to study or work (84%) or with the statement that AIDS is a public health problem (98.7%). The majority of the respondents (87%) said that the mass media including radio, television and newspapers were the main source of their information about HIV/AIDS. The findings from this study indicate that although misconception exist among Iranian about AIDS, in general they have fairly good knowledge and have positive attitudes towards AIDS and people with AIDS. Such findings suggest that prevention programs should be encouraged and these might have the potential role to limit the emergence of Iran's HIV/AIDS epidemic.