The present study is designed to analyze change in individual behavior problems of children. Several hundred children from an outpatient clinic were given the Child Behavior Checklist (CBCL: Achenbach) which is a standardized instrument for assessing children's problems and competencies. Correlations were performed between behavior items reported on the CBCL at intake and follow-up to assess stability and change in behavior over the course of treatment. The findings indicate that the controversy over the relative stability or lability of individual differences in behavior cannot be answered in all-or-none fashion for clincally important behaviors of childhood.