This article describes how job analysis, a method commonly used in personnel research and organizational psychology, provides a systematic method for documenting program staffing and service delivery that can improve evaluators' knowledge about program operations. Job analysis data can be used to increase evaluators' insight into how staffs administer programs and provide program services, interpretation of outcome data, make comparisons across programs, and assessment of programs' transferability and replication potential. Because of the central role that staffs play in the delivery of client services and client experiences, job analysis has particular promise for evaluating human services and social welfare programs. This article posits that with little added effort, job analysis can be integrated into traditional evaluation activities and the benefits of this addition will be significant. A basic job analysis methodology is described using an example of its application as part of an evaluation of a prisoner reentry program. (Contains 3 tables and 3 figures.)