With HCI researchers conducting studies in increasingly sensitive and difficult settings, ethics is emerging as a key concern for the HCI community. New technologies are now being designed and evaluated in settings that involve vulnerable or marginalized participants and that can be emotionally challenging for researchers. Research in these settings can produce complex ethical dilemmas that are often emergent, diverse, and highly contextualized. In addition, there may be discrepancies between the realities of HCI fieldwork and the formal and often rigid processes of obtaining ethics approval in research institutions. Given these issues, it is important for researchers to communally reflect on ethical encounters in HCI research. This workshop will provide a forum for researchers to share experiences about ethical challenges they have faced. These discussions will be used to develop a handbook of practical lessons representing the breadth and depth of ethical issues emerging in HCI research in sensitive settings.