The "Rating Scale of Impairment" (RSI; Goldstein & Naglieri, 2016b) is a norm-referenced measure of functional impairment. The RSI measures impairment in six domains, as well as overall impairment, based in part on the International Classification of Functioning, Disability, and Health. Functional impairment, as defined by the ICF and as measured by the RSI, does not emphasize pathology or lead to a diagnosis. However, when used with other sources of information such as developmental history, medical information, and other assessments, information from the RSI can help in guiding diagnostic decisions and in developing treatment plans. The RSI can be completed by a parent or teacher, and having both types of respondents complete the RSI provides a more comprehensive assessment of impairment across multiple domains and settings. On the RSI, respondents are instructed to respond based on behaviors observed during the past 4 weeks, indicating the frequency with which they have observed various behaviors using a 6-point scale. Three report types can be generated using the online scoring program: Interpretive Report (provides results from one administration, including a comparison to the standardization sample), Progress Monitoring and Treatment Effectiveness Report (provides an evaluation of score changes for the same rater over time), and Comparative Report (provides an analysis of scores from different raters). While understanding a youth's symptoms is important (particularly for diagnosis), it is also necessary to assess impairment to understand the impact of a condition and to identify targets for intervention. The author found that the RSI is well-suited to contribute to the assessment of impairment.