The Mindfulness Attention Awareness Scale (MAAS) for adults is a widely-used scale for measuring mindfulness, specifically reflecting the frequency of mindless states since all items are negatively worded with higher scores indicating less mindlessness. The MAAS was developed by Brown and Ryan in 2003 and focused on the attention and awareness aspects of mindlessness as defined by psychological theories and constructs rather than Buddhist origins of mindfulness. Items were developed based on unspecified previous publications and scales about mindfulness and the authors’ personal experiences to present accessible, everyday examples of mindlessness. The MAAS has been validated in multiple groups and languages, including clinical populations with psychiatric disorders, and extended to adolescents and children. With strong test-retest reliability and convergent and criterion validity, the MAAS showed expected relationships with positive and negative affect, quality of life, emotion regulation strategies, and other constructs. However, the MAAS has been criticized for indirectly rather than directly measuring mindfulness (all items are negatively worded and then reverse-scored) and containing a single factor structure, thus potentially omitting other aspects of mindfulness. Accordingly, the MAAS may be less sensitive to post-intervention changes than other measures, and relationships between the MAAS and meditation, yoga, and mindfulness training remain to be assessed. Finally, the MAAS is thought to reflect trait mindful awareness, and there is a distinct scale for state mindful awareness, but the extent to which the scale measures trait versus state remains to be established.