Informed consent is crucial in research, but potential participants may not all speak the same language, posing questions that have not been examined concerning decisions by institutional review boards (IRBs) and research ethics committees' (RECs) about the need for researchers to translate consent forms and other study materials. Sixty US IRBs (every fourth one in the list of the top 240 institutions by The National Institutes of Health funding) were contacted, and leaders (eg, chairs) from 34 (response rate=57%) and an additional 12 members and administrators were interviewed. IRBs face a range of problems about translation of informed consent documents, questionnaires and manuals-what, when and how to translate (eg, for how many or what proportion of potential subjects), why to do so and how to decide. Difficulties can arise about translation of specific words and of broader cultural concepts regarding processes of informed consent and research, especially in the developing world. In these decisions, IRBs weigh the need for autonomy (through informed consent) and justice (to ensure fair distribution of benefits and burdens of research) against practical concerns about costs to researchers. At times IRBs may have to compromise between these competing goals. These data, the first to examine when and how IRBs/RECs require researchers to translate materials, thus highlight a range of problems with which these committees struggle, suggesting a need for further normative and empirical investigation of these domains, and consideration of guidelines to help IRBs deal with these tensions.