Transcranial direct current stimulation (tDCS) is a brain stimulation technique known for its relative safety and minimal invasiveness. tDCS has demonstrated efficacy as a potential treatment for certain neurological disorders, such as Parkinson’s disease, and has been shown to enhance a range of cognitive abilities under certain contexts. As a result, this technique has captured the interest of both the research community and the public at large. However, efforts to gather information about the effects of tDCS on the brain are (...) still in their infancy, leading to concerns about informed consent as it pertains to the possible risks associated with tDCS treatment. The ability to purchase tDCS equipment in the form of commercial, direct-to-consumer devices, generates even more cause for ethical concern, given the unknowns surrounding this technology and its potential broader societal impact. Previous research has touched on the many ethical issues raised by the emergence of this technology, including under what circumstances its use is justifiable and appropriate. In this paper, we survey recent normative and empirical works pertaining to the ethics of tDCS with the goal of summarizing the current state of ethical debate surrounding its use in the contexts of both therapy and cognitive enhancement, with a particular emphasis on the latter. Our analysis of the collected research finds that issues pertaining to user safety are paramount within existing scholarship; that tDCS use in children is an emerging area of concern entailing special considerations; and that regulatory bodies and legal agencies have struggled to implement appropriate, impactful regulation pertaining to tDCS and related technologies in order to balance public welfare against individual autonomy. This analysis will facilitate future efforts to develop bioethical approaches to tDCS by highlighting the ethical dimensions of tDCS prioritized in existing literature and identifying areas where further ethical consideration is needed. (shrink)