Epigenetic testing is one of the most significant new technologies to provide insight into the behavioral and environmental factors that influence the development and reconfiguration of the human genetic code. This technology allows us to identify structural changes in the genome that occur due to exposure to a wide variety of substances including alcohol, tobacco, and cannabis. The information gained can be used to promote health but it also raises a variety of ethical, legal, and social issues. As society progresses in understanding the epigenetic mechanisms of substance use and addiction, there is an opportunity to use these use this knowledge to enable medical, behavioral, and environmental interventions to alleviate the burden of addiction. This article describes the ethical issues associated with use of epigenetic testing for alcohol, tobacco, and cannabis and the implications of this technology. A further review of the scientific basis for the relevance of epigenetics is found in the accompanying article by Philibert and Erwin in this issue. Copyright © 2015 John Wiley & Sons, Ltd.