In this article, we brief ly review the etiology of Attention Deficit Hyperactivity Disorder (ADHD) and describe the most current scientifically supported theory about the nature of this disorder. Based on the research literature, several organizations have established standards of care for its diagnosis and treatment, which involves a multimodal strategy for treatment at the biological, individual, family, school, and community levels. Assessment and treatment guidelines are provided for Marriage and Family Therapists (MFTs), and specific areas of competency are proposed for MFTs who are working with children who have ADHD.