The content of this guide was derived from ongoing work of a working group on growth models coordinated and facilitated by the SLDS Grant Program's State Support Team. The Statewide Longitudinal Data Systems (SLDS) Grant Program was asked by several states to review current growth models with the goal of determining the impact of different models on longitudinal data systems and capturing some best practices that states are using in the implementation process. From July 2011 through February 2012, representatives from Colorado, Arkansas, Ohio, Iowa, Pennsylvania, Delaware, and Florida participated in a working group session and follow-up discussions facilitated by members of the State Support Team (SST). This working group allowed states to more easily discuss and share strategies, best practices, and challenges related to the use of growth models. Specifically, these states have provided the following information to the SST in response to questions about their specific growth model(s) related to: (1) types and purposes of growth model(s) used; (2) description of model(s) used; (3) data elements required for each model; and (4) issues and barriers experienced during development, implementation, or use.