A category system was developed for describing the classroom behavior of earth science teachers. Video tape recordings were made of a random sample of 16 junior high school science teachers in Franklin County, Ohio. Classification of behaviors resulted in four major dimensions: Content Development, Management, Facilitating, and Classroom Climate. Twenty-nine subcategories were identified, each of which included both verbal and non-verbal behaviors. Four indices were developed by combining subcategories and expressing behaviors as ratios: Climate index, Process index, Interaction index, and Instructional index. The instrument was field tested in eight ninth-grade earth science classes, together with an instrument developed in a companion study for describing student behaviors. Two sets of video tape equipment were used for simultaneous recording of the behavior of the teacher and a sample of students. Teacher behaviors are described in terms of the instrument, and significant correlations between teacher and student behaviors are reported. (EB)