Forecasting is needed to help juvenile corrections personnel provide services that are appropriately designed and targeted to meet present and future needs of detainees. The Juvenile Institution Forecasting (JIF) model is the main focus of this report. It covers sources of data, likely difficulties in assembling data, methods of scenario development, among other factors. The model's flexibility accommodates "what if" questions and changing trends, and provides useful and timely advice to planners and policymakers. Appendixes include a Fortran listing of the JIF model, definitions of key variables, tabular examples of input data, and a sample scenario computer run using artificially generated data. Tables, 5 figures.