Currently, states are examining early childhood for its potential benefits to K12 and postsecondary education. However, these benefits are difficult to assess because of incomplete early childhood data in statewide longitudinal data systems (SLDSs). The need for data can pressure state education agencies (SEAs) to quickly increase the collection of--and access to--early childhood data. However, in order to successfully facilitate the use of these data, SLDS staff must proceed thoughtfully. Careful planning of early childhood data use, followed by the creation of products and resources that meet user needs, and ongoing support of these users will help to ensure that the data inform key early childhood decisions. This document is the third of three publications based on the State Support Team (SST)-designed framework on Early Childhood Data Use. The first two publications, Planning for Early Childhood Data Use and Early Childhood Data Use: Create Phase, are available online at http://nces.ed.gov/programs/slds/publications.asp. This publication examines the Support phase of the Early Childhood Data Use Framework (see Figure 1) as illustrated by experiences of SLDS leaders in Minnesota and Missouri. It also explores lessons learned from existing early childhood and K12 education research that could be applied to future early childhood data use projects. (author abstract)