This manual provides guidance and documentation for users of the longitudinal kindergarten-fourth grade (K-4) public-use data file of the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11 (ECLS-K:2011), which includes the first release of the public version of the third-grade data. This manual mainly provides information specific to the third-grade round of data collection. The first chapter provides an overview of the ECLS-K:2011. Subsequent chapters provide details on the third-grade data collection instruments and methods, including a description of how the third-grade data collections differ from the earlier rounds; the direct and indirect child assessments; the sample design; weighting procedures; response rates; and data file content, including composite variables.