Examined associations between effortful control temperament and externalizing problems in 220 3-year-old boys and girls, controlling for co-occurring cognitive and social risk factors. We also considered possible additive and0or interactive contributions of child dispositional anger and psychosocial adversity, and whether relations between effortful control and early externalizing problems were moderated by child gender. Individual differences in children's effortful control abilities, assessed using behavioral and parent rating measures, were negatively associated with child externalizing problems reported by mothers, fathers, and preschool teachers. These associations were not overshadowed by other cognitive or social risk factors, or by other relevant child temperament traits such as proneness to irritability. Further analyses revealed that associations between externalizing problem behavior and effortful control were specific to components of child problem behavior indexing impulsive-inattentive symptoms. Thus, children's effortful control skills were important correlates of children's early disruptive behavior, a finding that may provide insight into the developmental origins of chronic behavioral maladjustment. Problems of aggression, impulsivity, and inattention, often labeled externalizing symptoms, represent the most common forms of childhood maladjustment~IOM, 1989; Kazdin, 1995!. Once established, these problems tend to be chronic, placing children at risk for a wide range of negative adaptational outcomes including academic failure, rejection by peers, conflicted interactions with parents, siblings, peers, and teachers, and delinquent behavior~Caspi & Moffitt, 1995; Coie & Dodge, 1998; Patterson, Reid, & Dishion, 1992!. How early in life do these problems become established? Recent research has shown that serious externalizing problems can be identified in the toddler and preschool years Keenan & Wakschlag, 2000!, and that individual differences in externalizing behaviors persist at moderate levels across the transition from early to middle childhood~e.g.,