With the desegregation processes of services for people with intellectual disability (ID) that is taking place in most Western countries there is a need for more knowledge related to the prevalence of behavior problems among people living in community settings. This study investigates the prevalence of behavior problems among 140 adolescents and adults with ID living in 5 municipalities in Norway using the Aberrant Behavior Checklist (Aman & Singh, 1986, 1994). Twenty percent of the sample were reported to show severe behavior disorder or "challenging behavior," and this gives a prevalence for challenging behavior of 63.6 people per 100,000 base population. On the average, people showing challenging behavior had 7 behaviors rated as severe problems. A total of 60 participants were reported to have moderate or severe behavior problems, giving a prevalence for moderate and severe behavior problems of 136.3 per 100,000 base population. There were more people with profound ID and more people with autism in the group with challenging behavior and more people with Down syndrome in the group with mild or no problems. Those with severe behavior problems were perceived to be significantly less satisfied with their life situation than people without severe behavior problems. Challenging behavior seems to have a significant negative impact on the quality of life of people with ID. The results of this and other studies of challenging behavior among individuals with ID who live in areas with different service structures, using base population information, are important for analyzing the impact of reforms and different service systems on the life quality and well-being of people with ID. (Contains 5 tables.)