Community-based assessment of HIV prevalence and behavioural risk factors is the basis for deciding priorities of prevention and care programmes. Here, upholding the human rights of participants in assessment is of utmost importance. The objective of the paper was to describe the process of implementation of an epidemiological survey to assess HIV-related behavioural and biological factors in Chennai city in South India and to suggest an ethical framework for conducting similar assessment activities in developing-country settings. A survey was conducted with participation from residents (n=1,659) of low-income urban communities (slums) as part of a community-based HIV/STD-prevention trial. Administration of the survey was preceded by extensive community contact and household visits to inform community members about the trial and assessment activities. Formative research further strengthened rapport with community, highlighted community concerns, and identified HIV-related risk behaviours that informed questionnaire design. The process of obtaining informed consent began before assessment activities and provided an opportunity for individuals to discuss participation with their families and friends. Privacy during assessment, comprehensive follow-up care for those who tested positive for HIV/STDs, such as nutritional and prevention counselling, referral services for opportunistic infections, and antenatal-care options for pregnant women increased trust and credibility of the project. The sustained availability of trial staff to facilitate access to resources to address non-HIV/STD-related felt-needs further strengthened participation of the community members. These resources included liaison services with local government to obtain public services, such as water and electricity and resources, to address concerns, such as alcohol abuse and domestic violence. Based on this experience, an ethical framework is suggested for conducting HIV epidemiological risk assessment in developing countries. This framework discusses the role of community participation, transparent and comprehensive informed consent, timely dissemination of results, and access to follow-up care for those living with HIV/STDs.