An overview of the jail overcrowding problem emphasizes that local criminal justice officials have broad discretion in deciding which arrestees are detained in custody and for how long, but few make these decisions according to a coordinated plan. Also covered are definitions of overcrowding, a method for calculating the jail's average daily population, and conventional responses to overcrowding. The report describes prerequisites for adopting the jail population management approach and how to create a planning mechanism. It comments that this effort must have project status, sufficient time to collect data, adequate staffing, and an appropriate operating budget. Specific components of the planning process include a project initiator, a sponsor group, a facilitator, and a jail population management board composed of representatives from criminal justice and social welfare agencies. The report also outlines job descriptions for staff, time requirements, and cost estimates. The final section explains how the planning mechanism can be used to implement a jail population management project, focusing on three major tasks: producing a system description; collecting and analyzing descriptive, statistical, and fiscal data; and preparing and launching the actual plan. The appendixes contain materials from the LEAA projects which illustrate budgets, data collection strategies, study designs, and agendas, along with eight references.