Neuromarketing has recently generated controversies concerning the involvement of medical professionals, and many key questions remain-ones that have potentially important implications for the field of psychiatry. Conflicting definitions of neuromarketing have been proposed, and little is known about the actual practices of companies, physicians, and scientists involved in its practice. This article reviews the history of neuromarketing and uses an exploratory survey of neuromarketing Web sites to illustrate ethical issues raised by this new field. Neuromarketing, as currently practiced, is heterogeneous, as companies are offering a variety of technologies. Many companies employ academicians and professionals, but few list their clients or fees. Media coverage of neuromarketing appears disproportionately high compared to the paucity of peer-reviewed reports in the field. Companies may be making premature claims about the power of neuroscience to predict consumer behavior. Overall, neuromarketing has important implications for academic-industrial partnerships, the responsible conduct of research, and the public understanding of the brain. We explore these themes to uncover issues relevant to professional ethics, research, and policy. Of particular relevance to psychiatry, neuromarketing may be seen as an extension of the search for quantification and certainty in previously indefinite aspects of human behavior.