This guide is intended to assist states and service delivery areas (SDAs) in addressing the new oversight responsibilities and opportunities stipulated by the Job Training Partnership Act (JTPA) with respect to net impact evaluations. It is divided into two main parts. The first part, which deals with issues in evaluating costs and benefits, covers the following topics: the distinction between benefit-cost and effectiveness-cost evaluation; identification and measurement of benefits and costs (general taxonomy of benefits, general taxonomy of costs, practical problem of cost estimation, introduction to economic cost theory, cost estimation at the service delivery area and state levels); and basic methods and issues in benefit-cost analysis. Examples of total, average, and marginal cost functions and a sample federal report for obtaining new data are appended. The second part of the guide, which examines the debate over experimental versus quasiexperimental approaches to assessing net impact, discusses the context of the debate, scientific trade-offs in the debate, and organizational and political trade-offs. Appendixes include definitions of the major concepts involved, some sources and kinds of bias, and a research design continuum. (MN)