A state contacted the Center on Enhancing Early Learning Outcomes (CEELO) for guidance in developing a definition of "reading proficiency" and what it means to "read on grade level by third grade." The state also requested information on how national sources or states define and measure proficiency. The state was particularly interested in national perspectives pertaining to the development of shared meaning for the terms, as well as any evidence of individual state-adopted definitions of reading proficiency. "Literacy" is most often described as the skills and knowledge that are necessary to learn to read, including phonological awareness/beginning reading, listening, speaking, and writing. "Reading" is described as a set of interrelated skills needed to learn from reading in order to comprehend meaning from varied texts. "English Language Arts" generally refers to the skills needed to comprehend and communicate effectively. This report provides selected resources regarding national and state definitions to inform a definition of reading proficiency and approaches measuring proficiency.