This qualitative study sought information about the content, nature, and diversity of teachers' beliefs and principles. Selected studies involving the beliefs of teachers in the areas of curriculum theory and innovation, decision making and thinking, and improving teaching are discussed and analyzed. A discussion of the study's methodology points out that there are numerous problems in obtaining information in an area which is by nature somewhat elusive. An established methodology, the Repertory Grid Technique, developed by G. A. Kelly in 1955, is described. Detailed discussion is presented of 4 of 14 middle school teachers' interview responses. The Repertory Grid developed from interviews with one teacher is displayed. Some generalized conclusions are drawn on the efficacy of the Repertory Grid Technique in research of this kind and on its possible value in determining teachers' points of view. (JD)