Teaching is an applied science derived from research in human learning and behavior. The science of teaching is based on cause-effect relationships existing in three categories of teacher decisionmaking (content, learner behavior, and teaching behaviors). Several "templates" can be used to describe, interpret, and evaluate either formatively, to improve the teaching process, or summatively, to categorize teaching quality. One template is an examination and interpretation of teacher decisions and behaviors in terms of the three previously mentioned categories. A second template is lesson design, and the third template is the TA III (Teaching Appraisal for Instructional Improvement Instrument). This instrument was developed to document changes in teachers' decisions and behaviors and to validate positive influence of those changes in student learning gains. A principal's responsiblities for teacher evaluation are also discussed; the role of preservice and inservice education receives attention. Responses to this article are offered by Susan B. Leahy and Arthur L. Costa. (JMK)