RESUMEN
UNLABELLED: Researchers who investigate social and economic determinants of health often interact with vulnerable and marginalized populations. Great care must be taken to conduct research studies involving vulnerable persons in a manner consistent with accepted ethical principles in order to protect participants from exploitation, to build capacity, and to promote wellbeing. Children form a particularly vulnerable group, especially those who do not enjoy the protection of parents or guardians. METHODS: A research project which studied South African Sunnyside's street children was used as a case study to illustrate ethical issues surrounding research with vulnerable populations. DISCUSSION: The participants in the case study lacked the age of majority and were without any legal guardian. The researchers experienced considerable difficulty in obtaining ethical approval to conduct the study. The street children, at first, were not allowed to give informed consent for the study because of their minor age. Ethical principles of autonomy, disclosure, competence and understanding, consent and voluntariness, beneficence and non-maleficence, and justice are described and applied to this case study involving street children in a South African neighbourhood. It is suggested that by working within an ethical framework, the safety of research participants will be assured and the quality of the research will be enhanced.