In determining the influence of various factors on outcome, one must keep in mind that these parameters do not act alone but probably exert their influence in a cumulative and interactive manner. Thus, characteristics of the child such as severity of symptoms, comorbidity, and IQ interact with family parameters such as parental pathology, socioeconomic status, family adversity, and treatment to influence long-term outcome. Some of these variables (e.g., comorbid CD, low IQ, parental pathology) have been important in influencing negative outcome. Treatment, particularly stimulant treatment, has been shown to be effective in many short-term studies, but the long-term impact of treatment remains uncertain. The continuation of treatment may be crucial in influencing positive long-term outcome. Particular treatment modalities or combinations (e.g., multimodal treatment) may be required for specific patient subgroups (e.g., subjects comorbid for LD, CD, or anxiety; subjects with low socioeconomic status or high parental pathology). Research in the area continues to evolve. New findings hopefully will continue to improve both the quality of life for patients and families and positive influence of long-term outcome.