The 6-year developmental course of parent-reported problem behavior in an epidemiological sample of 936 children assessed with the Child Behavior Checklist at 2-year intervals was determined. Children who were scored in the deviant range of the total problem score at time 1 were nine times more likely to be scored deviant 6 years later than were children who were not deviant at time 1 (odds ratio 9.0). Of the deviant children at time 1, 33% were deviant at time 4. There was no difference in the persistence of externalizing versus internalizing problems. This underscores the notion that internalizing problems should not be disregarded. Although this study demonstrated moderate stability of problem behaviors across a 6-year interval, children's problem behaviors should not be regarded as static. Many children showed changes in their level of functioning across time. However, extreme changes were the exception rather than the rule.