States increasingly are incorporating Kindergarten Entry Assessments (KEAs) into their comprehensive assessment systems with the goal of helping educators identify gaps in children's competencies, target instruction to children's individual needs, engage parents to better support their child's learning, and identify needs for expanding and improving early learning opportunities. In 2010, seven states collected KEA data for the purposes of aggregating data at the state level (Daily, Burkhauser, and Halle 2010). By 2014, 29 states were engaged in development and use of KEAs with support from federal programs such as Race To the Top-Early Learning Challenge (RTT-ELC) grants and Enhanced Assessment Grants (EAG). This descriptive study examines the development and early implementation of KEAs in 12 districts and 23 schools within four RTT-ELC states (Maryland, Oregon, Pennsylvania, and Washington) during the 2014-15 school year. This was the first year of KEA implementation in Maryland and Pennsylvania, the second year of KEA implementation in Oregon, and the third year of KEA implementation in Washington, so findings reflect the early implementation of these assessments. The study is intended to help states learn from the experiences of other states as they work to develop and implement their own KEAs and to use KEAs to improve instruction and learning. [For this study's "Results in Brief," see ED613416.]