The same 18 symptoms of ADHD are listed in the Diagnostic and Statistical Manual, Version IV (DSM-IV) published by the American Psychiatric Association and in the International Classification of Diseases, Edition 10 (ICD-10) manual published by the World Health Organization as criteria for hyperkinetic disorder (HKD). These behaviors can be defined as psychopathology that is present or absent (see Table 1) or as the extremes of underlying dimensions that encompass normal behavior (see Table 2). In our research program, we have used rating scales to collect norms for these behaviors in school wide samples, using the Swanson, Nolan and Pelham (SNAP) rating scale of psychopathology and the Strengths and Weaknesses of ADHD-symptoms and Normal-behavior (SWAN) rating scale of underlying dimensions of attention and action. These norms can be used to quantify statistical abnormality based on severity as judged by parents and teachers (see Fig. 1). (author abstract)