This manual provides guidance and documentation for users of the kindergarten (or base year) data of the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11 (ECLS-K:2011). It begins with an overview of the ECLS-K:2011. Subsequent chapters provide details on the study data collection instruments and methods; the direct and indirect child assessment data; the sample design; weighting procedures; response rates; data file content, including composite variables; and the structure of the data file. Data for the ECLS-K:2011 are released in both a restricted-use and a public-use version. This manual, which has been developed for public dissemination and use with the public version of the data, is almost identical to the manual released with the kindergarten restricted-use file. The ECLS-K:2011 is following a nationally representative sample of children from kindergarten through their elementary school years. It is a multisource, multimethod study that focuses on children's early school experiences. It includes interviews with parents, self-administered questionnaires completed by teachers and school administrators, and one-on-one assessments of children. During the kindergarten year, it also included self-administered questionnaires for nonparental before- and after- school care providers. The ECLS-K:2011 is the third study in the Early Childhood Longitudinal Study (ECLS) program, which comprises three longitudinal studies of young children: the Early Childhood Longitudinal Study, Kindergarten Class of 1998-99 (ECLS-K); the Early Childhood Longitudinal Study, Birth Cohort (ECLS-B); and the ECLS-K:2011. Three appendices are included: (1) Data Anomalies and Errata; (2) Creating a School-Level File; and and (3) Supplemental Guide for the Kindergarten-First Grade Public-Use Data File.