This paper describes the development and intended uses of the Early Grades Mathematics Assessment (EGMA), which measures essential early mathematical knowledge and skills that are foundational to more sophisticated mathematical abilities, predictive of later achievement, and teachable. Administering the EGMA can provide policy makers, practitioners, and researchers with information about whether existing educational policies, curricular reforms or programs, and instructional interventions are supporting students in reaching important goals in mathematics. We highlight the utility of the EGMA results in three abbreviated illustrations of implementation studies in low-income countries. Recommendations for policy makers, practitioners, and researchers are provided.