The Depression Anxiety Stress Scales (DASS) was created as a multifaceted screening instrument for depression, anxiety, and stress with the overall score representing an overarching psychological distress. Globally, the DASS has become one of the most extensively used assessment tool for depression, anxiety, and stress within both general and clinical populations. In this chapter, the theoretical background of anxiety, depression, and stress are outlined, followed by an account of the scale’s development and inceptive validation. The original exploratory and confirmatory factor analysis results are then presented to support the original validation of the scale, and its psychometric properties; more recent studies are also examined which generally support robustness of the DASS. Rasch analysis and ordinal-to-interval tables are provided, demonstrating good reliability and robust psychometric properties of the scale’s overarching distress construct as well as of each of the subscales. Overall, the DASS has been shown to demonstrate good psychometric properties across cultures with versions translated and validated in several languages.