Given the high prevalence of child neglect among maltreatment subtypes, and its association with exposure to additional environmental adversity, understanding the processes that potentiate child neglect and link neglect to subsequent child externalizing psychopathology may shed light on key targets for preventive intervention. Among 170 urban low-income children (ages 4-9) and their mothers, this 5-year prospective study examined the effects of early neglect severity and maternal substance abuse, as well as neighborhood crime, on children's later externalizing behavior problems. Severity of child neglect (up to age 6 years) mediated the relation between maternal drug dependence diagnosis (MDDD), determined at children's age of 4 years, and children's externalizing behavior problems at age 9. Rates of neighborhood crime mediated the link between presence of child neglect and children's externalizing behavior problems. The roles of MDDD, child neglect, and community violence in the development of child psychopathology are discussed in terms of their implications for intervention. Abstract published by arrangement with Sage Journals.