Evaluation provides a means to facilitate treatment decisionmaking. In special education, evaluation must assess what the student needs to be taught and how it will be taught. To be meaningful, such evaluation must have appropriate content, be based on valid standards (generally behavioral criteria or criteria for acceptable performance that assess proficiency), and use appropriate measures. Measures should be clearly linked to curriculum content and behavior domains. A task analytic model of evaluation is recommended for correctional special education. The model is based on the premise that students fail at a task because they are missing one or more essential task components. The evaluation requires fact-finding, hypothesizing, validating, and decisionmaking to identify student needs and devise instructional objectives to meet them. This model can be applied to both academic evaluations such as reading, and social skills evaluations. By maintaining a curricular focus and employing specific task procedures for sampling behaviors and establishing standards, functional evaluators can set the stage for immediate and positive changes in student learning. The task of the special educator in a medium-security prison is described. 3 tables, 7 figures, and 11 references.