The 4-year stability in problem behaviors assessed with the Child Behavior Checklist (CBCL), and their predictive validity with regard to poor outcome variables was studied in 1052 4-12-year old children from a general population sample. Irrespective of sex and age, the scores on the CBCL of some 44% of the children remained above the 90th percentile over the 4-year time interval. Externalizing problem behavior tended to show somewhat greater stability than internalizing problem behavior. High initial levels of both internalizing and externalizing problems, and persistence of problems were predictive of referral to mental health services. Referral to special education was higher for younger boys with high initial attention problems and school problems. Police contacts occurred more often in older boys with high initial aggression scores.