Twenty-one parents participated in a Collaborative Problem Solving (CPS) parent group targeting children's challenging behavior; 18 parents were in a waitlist control group. All parents completed pre- and post-treatment measures on CPS learning targets, their child's behavior, and relationship quality, and parents in the treatment group completed measures six months later. Only parents learning CPS reported significant improvements on learning targets and conflict, and changes were sustained six months later. Children's behavior improved significantly in the treatment group by six-month follow-up. These findings support CPS parent groups as an economical and effective approach for parents of children with behavioral difficulties. [ABSTRACT FROM AUTHOR]