Rating scales are valuable tools in both assessment and treatment monitoring. However, caution in their use is indicated because of several types of rater errors. Recent large-scale normative studies provide a set of instruments that cover child, adolescent, and adult ages, with separate gender norms and large representative samples. By including DSM-IV symptoms for ADHD in a proposed nationwide standardization of parent, teacher, and self-report scales, it is apparent that the proposed subtypes of ADHD are reasonable; however, item content in this standardization is somewhat broader than that proposed by DSM-IV. Empirical indexes were created and cross-validated, providing powerful discrimination between ADHD and non-ADHD samples. Separate scoring for the traditional DSM subtypes of ADHD allows both categorical and dimensional measures to be used in assessment and treatment monitoring.