Preschool education is increasingly being recognized as an integral part of efforts to ensure that all children enter school ready to learn and as a way to help close the achievement gaps that exist at the time children enter kindergarten. Such efforts are growing across the country. According to the most recent data, 54 different preschool initiatives in 40 states serve over one million children, almost double the number served eight years earlier. As these programs and efforts to monitor them have grown, a common focus is on documenting children's learning outcomes. Assessing young children, however, presents particular challenges. This report identifies and describes state-funded Pre-K assessment policies and programs operating in 2012 and discusses the special challenges related to assessing young children. A table for specific child outcome measures that must or may be used as per Pre-K Policy is appended. (Contains 3 tables and 95 footnotes.)