A CHAPTER on teaching in an issue of the REVIEW devoted to curriculum planning and development is justified more by theoretical need than by the existence of research which can clearly be categorized under the label, "teaching." Educators turn to many other categories which pull together information and ideas related to teaching. In recent REVIEW issues, Ellis (14) examined writings dealing with instructional procedures in secondary schools, and Leavitt (33) reviewed the literature on teacher-pupil relationships in elementary schools. In the third edition of the Encyclopedia of Educational Research, writings related to teaching were summarized by Stiles (55) under "Instruction" and by Wingo (63) under "Methods of Teaching."In summarizing literature on different aspects of the same phenomena, Barr and Jones (3) stated that the primary factors of teaching have been ignored and that only surface aspects have been studied. This opinion is not uncommon today. Dodes (12), reviewing studies from 1900-1955 in order to suggest measures for solidifying the background of pedagogical knowledge, concluded that the dearth of scientific evidence is the result, in part, of ready acceptance of mere opinion and of a lack of clarity in terminology. The need to study teacher behavior in a context of theory was emphasized by Ryans (47), and it is this recurring theme which justifies inclusion of a chapter on teaching in this issue of the REVIEW.Whatever schools do or are expected to do, most educators would agree that teachers are expected to, and do, teach. Of all researchers in education, those who claim the curriculum as their field of inquiry presumably have the greatest interest in teaching. One would assume, therefore, that curriculum research would focus major attention on teaching in order to understand it and thereby gain greater control over it. However, teaching has seldom been studied by curriculum researchers as a social or educational phenomenon in its own terms. For example, the comprehensive review of 25 years of educational research (1) published in 1956 reported not one study focused directly on teaching.During the three-year period of this review, researchers have continued to study (a) effectiveness of teaching and prediction of teacher success, (b) teacher-student relationships, and (c) methods and styles of teaching. There is, however, a growing interest in the study of teaching as such.246