This brief report provides a demographic profile of the students who attended kindergarten in the United States in the 2010-11 school year using data from the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11 (ECLS-K:2011). The ECLS-K:2011 cohort includes students in public and private schools across the United States, students who attended part-day and full-day kindergarten programs, and students who were attending their first year of kindergarten as well as those who were repeating kindergarten. The analyses presented in this report focus on the 3.5 million students who were attending kindergarten for the first time in the 2010-11 school year. Approximately 5 percent of the students in the ECLS-K:2011 cohort were repeating kindergarten and are not represented in the findings in this report. The ECLS-K:2011 is a longitudinal study that will follow a nationally representative sample of students from their kindergarten year to the spring of 2016, when most of them are expected to be in fifth grade. During the first year of data collection, when all children were in kindergarten, data were collected in both the fall and the spring. Approximately 18,200 children enrolled in 970 schools during the 2010-11 school year participated during the kindergarten year. The study will provide information on students' status at entry to school, their transition into school, and their progression through the elementary grades. The longitudinal nature of the ECLS-K:2011 data will enable researchers to study how a wide range of family, school, community, and individual factors are associated with educational, socioemotional, and physical development over time. Information is being collected from the students, their parents/guardians, their teachers, their school administrators, and their before- and after-school care providers. Readers are cautioned not to draw causal inferences based on the results presented. It is important to note that many of the characteristics examined in this report may be related to one another, and complex interactions and relationships among the characteristics were not explored in this report. The variables examined here are just a few of the several thousand that can be examined using the ECLS-K:2011 data. These findings are examples of estimates that can be obtained from the data and are not designed to emphasize any particular issue. In addition, the estimates presented in this report are based on a preliminary version of the ECLS-K:2011 restricted-use data. Estimates produced with the final restricted-use data file, or the public-use data file, may vary. Appended are: (1) Survey Methodology and Glossary; and (2) Standard Error Tables. (Contains 6 tables and 9 footnotes.) [Additional support for this paper was provided by the Administration on Children, Youth, and Families and the Office of English Language Acquisition.]