At the heart of the instructional supervisor's role is helping teachers learn and unlearn attitudes, concepts, and skills relevant to their jobs. Among the principles the supervisor must understand to provide this help are those relating to motivation, learning readiness, the learning climate, levels of aspiration, and reinforcement. Diagnostic supervision serves as a framework for facilitating teachers' learning and unlearning. Diagnostic supervision responds to individual needs, interest, and abilities in the context of institutional and community goals and priorities. The process has three phases: (1) recognizing needs, stating problems, and agreeing on objectives; (2) assessing attitudes, concepts, and skills; and (3) selecting or designing strategies. Diagnostic supervision is a useful concept for guiding supervisory practice, but can only be used effectively in a district that is ready for it. A districtwide program of supervision would account for the following components: (1) local, regional, and national expectations; (2) critical supervisory functions; (3) organizational structures; (4) multilevel planning; (5) specific supervisory strategies; (6) supervisory staff development; (7) analysis and evaluation of supervisory practice; and (8) the objectives of supervision. (PGD)