Thus, although an existing body of research has suggested that maltreatment is one of the most potent (and preventable) environmental influences on antisocial development, there remain persistent questions about the relative magnitude and impact of maltreatment in the general population, especially when controlling for inherited risk. We undertook this study to provide the first observation of the effects of maltreatment on the development of conduct problems in children using official-report maltreatment data in a large-scale epidemiologic twin sample.