This study investigated the characteristics of 106 children primarily referred for externalizing behavior problems and their families, and assessed the prediction of treatment outcome following a standardized short-term, cognitive behavioral group program. "Exploring Together" comprised a children's group (anger management, problem-solving and social skills training), a parents' group (parenting skills training, dealing with parents' personal, relationship and family-of-origin issues), and a combined children's and parents' group (to target parent--child interactions). The main predictors of reductions in externalizing and internalizing behaviors at home following treatment were children's pre-existing levels of these behavioral and emotional problems (children with higher levels improved most), and positive parent--child interaction. Higher pre-existing levels of behavioral and emotional problems and low levels of attention problems predicted greater improvement in post-treatment school behaviors. Implications of the findings for improving interventions for childhood behavioral and emotional problems are discussed.