Described is the development of an observation instrument that is designed to give a measure of the overall teaching strategy or style used by a teacher including both verbal and non-verbal interactions between teachers, students, and the physical materials which constitute the classroom environment. The instrument was developed to give a single rating of a teacher's style, representing his position on a continuum which can be described in very general terms with extremes defined as (1) expository-direct teaching and (2) inductive-indirect teaching. The instrument based on this model of teaching passed through several versions during its three years of development; however, in all versions, a rating of teaching style on a numerical scale is given for each one minute interval. Several versions of the instrument have been used in two studies of elementary school science teaching, one secondary science study, and one study of elementary school social studies. (BR)