Online charter schools -- also known as virtual charters or cyber charters -- are publicly funded schools of choice that deliver student instruction via telecommunications. Today, about 200 online charter schools are operating in the United States, serving about 200,000 students at the elementary, middle, and high school grade levels. Although online instruction is increasing rapidly, there have been few studies of their operations and effects. In innovative new research funded by the Walton Family Foundation, the National Study of Online Charter Schools offers a rigorous analysis of online charter schools and their effects. Mathematica Policy Research's report provides the first nationwide data and analysis of the operations and instructional approaches of online charter schools, based on data collected in a survey completed by 127 principals of online charter schools across the country and public data from the U.S. Department of Education.