The legitimate uses of new instruments for the selection and appraisal of principals, factors influencing use of these instruments, and safeguards to minimize misuse are discussed. Performance appraisal systems in education have been used legitimately to ensure that principals meet minimum performance standards, and for promotion. Another valuable function is in meeting professional development needs of principals. Data from appraisal instruments may be incorrectly or inadequately used. Use and misuse of instruments are influenced by: (1) the conceptual framework used; (2) the perspective of the test developer; (3) the perspective of the practitioner; and (4) links to factors influencing use. Safeguards that instrument developers and practitioners alike may use include: (1) an explicit and clear technical manual; (2) a standard system for processing data; (3) extensive field training of practitioners; (4) use of instruments as part of a battery of procedures for evaluation; and (5) caution about claims that any one instrument can define the ideal principal. (SLD)