||Existing research consistently links difficult early temperament and later externalizing behavior problems; however, the literature has shown that parental discipline style can influence this relationship. There are few studies that have considered this interplay of temperament and parenting in high-risk populations, including children who have been maltreated. Maltreatment alone is a public health concern and a source of trauma for those who are affected. Further, child maltreatment has been shown to place a child at greater risk for developing behavior problems. The current study examined the influence of harsh discipline and infant difficult temperament on the development of child externalizing behavior problems in an existing longitudinal sample of 1,148 infants who were the subjects of child welfare investigations (the National Survey of Child and Adolescent Well Being, NSCAW). Specifically, the examiner sought to determine if difficult temperament exacerbates the risk of harsh discipline or if harsh discipline mediates the association between difficult infant temperament and externalizing behavior problems in early childhood. Children included in the subsample for the current study were between 0 and 23 months of age at Time 1 data collection. Infant difficult temperament was measured at Time 1 with the Infant Behavior Questionnaire (IBQ) and harsh discipline was measured at Time 1 with the Parent-Child Conflict Tactics Scale (CTS-PC). The child's primary caregiver completed both measures. In the NSCAW sample, Time 1 data collection interviews took place approximately 3 to 6 months after the close of the Child Protective Services investigation. To measure childhood externalizing behaviors, the externalizing scale from the Child Behavior Checklist (CBCL) was used. Parents rated children's behavior on the CBCL 5 years after the close of the investigation, when children were between the ages of 5 and 7 years. Multiple regression analyses showed that both difficult temperament and harsh discipline predicted worse externalizing behavior outcomes; however, these two factors did not show a significant interaction. Mediation analyses further demonstrated an indirect effect through harsh discipline in the association between difficult temperament and externalizing problems. Findings extend the literature regarding infant difficult temperament and harsh discipline to children who have experienced maltreatment and help to illuminate areas that can guide early intervention efforts for children at risk.