Research on epigenetic mechanisms is gaining traction, yet is poorly understood by criminologists and behavioral scientists. The current objective is to review relevant studies of interest to behavioral scientists who study crime, and to translate admittedly challenging scientific information into text that is digestible to the average criminologist. Using systematic search procedures the authors identified and reviewed 41 studies of epigenetic mechanisms in psychiatric and behavioral phenotypes among humans. Findings revealed significant epigenetic effects in an assortment of genes that are implicated in the etiology of depression, suicidality, callous–unemotional traits, and chronic and intergenerational aggressive behavior. Several polymorphisms that mediate the HPA axis, neurotransmission, immune response, brain development, serotonin synthesis, and other processes were found. Although prescriptive knowledge based on epigenetic findings to date is premature, epigenetics is a new and exciting scientific frontier not too different in spirit from Lamarck's observations centuries ago. Copyright © 2015 John Wiley & Sons, Ltd.