Considerable evidence suggests that phonemic awareness is associated with the development of skilled reading. Consequently, it is recommended that beginning readers be assessed to ensure adequate development of phonemic awareness skills. When choosing an assessment method, reliability and validity, ease of administration and scoring, and cost-effectiveness should be considered. To meet these standards, a new phonemic awareness assessment measure, the Mountain Shadows Phonemic Awareness Scale (MS-PAS), was presented. This 20-item sound categorization task takes 20 minutes for an entire first-grade classroom. Reliability and validity data were good to excellent. It was recommended that the MS-PAS be used to identify students in need of explicit phonological awareness instruction or those who require more extensive individualized assessment. (Contains 3 tables and 1 figure.)