This chapter summarizes rates of maltreatment and discusses key theoretical models on the etiology of maltreatment. It proposes a model by which parent and child development may interact over time to increase risk for a maltreating environment. A maltreating environment is a complex system that is multiply determined. Two complementary theoretical models have contributed substantially to the field's understanding of the causes of maltreatment: Belsky's social-contextual process model and Cicchetti and colleagues' ecological-transactional model. The chapter reviews the literature that examines perpetrators' ages when they are most likely to commit abuse and neglect, and some of the reasons why developmental periods in parents' lives and their risk for psychopathology might be associated with risk for maltreatment. Finally, the chapter covers possible ways in which a maltreating environment is influenced by child characteristics over development, with a focus on child antisocial behavior.