Aggression and self injurious behaviors are associated with some clients with autism and other forms of pervasive developmental disorder. These behaviors are not well understood, and treatment interventions are often ineffective. This article describes these behaviors in terms of the underlying deficits of autism, suggesting that interventions may be more effective if targeted at the underlying causes of the actions. The article presents behaviors and underlying causes within an "iceberg" conceptualization with visible behaviors depicted as occurring "above the water line" and hypothesized causes hidden "below the water line" of the iceberg. Examples of clinical cases are presented to illustrate the usefulness of the conceptualization.