We review the effects of genes and family resources on families and children. Poverty increases children’s exposures to environmental risk factors such as child abuse, poor quality parenting, and suboptimal physical environment. These environmental risk factors interact with various genes to predict more behavioral problems in childhood. Relations between genes and environments are likely more complex than simple individual gene × environment interactions. In some cases, genetic or environmental factors may have different impacts in low- vs. high-SES groups. Finally, we speculate about biological mechanisms that may account for gene by environment interactions. Poverty and related environmental factors may interact with genes, which may lead to abnormal brain development as well as dysregulation in both neurotransmitters and neuroendocrine stress regulatory systems.