AbstractThis article describes a qualitative study of the beliefs and principles of one science teacher. The study employs the Repertory Grid Technique of Kelly (The psychology of personal constructs, New York: Norton, 1955). This technique is illustrated thoroughly by the case study, and ample segments from an interview with the teacher concerned are provided. All relevant information obtained from working with this teacher is used to establish the dominant beliefs held by her. The significance of the study is argued within the framework of curriculum and instructional innovation and implementation.