A process evaluation examines the theoretical bases for treatment strategies, the manner of implementing these strategies, the context of program operation, and the program's links with other criminal justice and therapeutic efforts. The process evaluation determines what happens to a client from entry into the program until discharge. It is also the process evaluation that determines whether and how programs are responsive to changing client needs and the shifting social and political dynamics within the community. A process evaluation can provide four pieces of otherwise missing information important in the assessment of any treatment effort: a detailed program description; changes from planned treatment strategies; analysis of the variables that explain program changes, failures, and successes; and an explanation of the reasons for program outcomes. This article discusses questions for conducting process evaluations, data sources for process evaluations, and who should conduct process evaluations. 4 references