Two hundred and ninety-three randomly-selected members of the staff of ICDDR,B: Centre for Health and Population Research were surveyed anonymously in June 1998, using a pre-tested and self-administered questionnaire, to assess their knowledge on, and attitude toward, human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS). All except 4 (1.4%) heard of AIDS. Main sources of information were radio and television (93%), newspapers and magazines (84.8%), posters and leaflets (70.2%), and friends (59.2%). About 94% of the respondents believed that HIV might spread in Bangladesh. Only 61.6% knew about the causative agent for AIDS. More than 96% had knowledge that HIV could be detected through blood test. The respondents were aware that unprotected sexual intercourse (92%), transfusion of blood and blood components (93.8%), sharing unsterile needles for injections (94.1%), and delivery of babies by infected mothers (82.7%) could transmit HIV. Similarly, the respondents had the knowledge that HIV infection could be prevented by using condom during sexual intercourse (85.5%), having sex only with an HIV-negative faithful partner (87.2%), avoiding transfusion of blood not screened for HIV (88.9%), and taking injections with sterile needles (86.5%). However, only 33.0% had the knowledge that HIV-infected persons can look healthy, and 56.4% were unaware of transmission through breastmilk. Most members of the staff, particularly at lower level, had misconceptions about transmission and prevention of HIV/AIDS. More than 40% of the respondents had the attitude that HIV-infected persons should not be allowed to work, while another 10% did not have any idea about it. The findings of the study suggest that the members of the Centre's staff have a satisfactory level of essential knowledge on HIV/AIDS, although half of them have poor attitudes toward persons with HIV/AIDS. Therefore, preventive strategy for the staff should be directed toward behaviour change communication.