Ethnographic methods were used to study interactions between a college instructor and his class. The data collection methods included classroom observations, videotape recordings, interviews, and questionnaires. The focus of the study was on co-occurring behavior patterns in student-teacher interactions during a "subject matter loop" (when the instructor was concerned with the students' understanding of and participation in the subject matter). A transcript was made of a segment of a college instructor's mathematics instruction. Analysis of the transcript and the accompanying verbal and nonverbal behaviors shows an instructional sequence composed of: (1) focusing the students' attention; (2) presenting information and stimulating thought; (3) revealing the "punch line," or the essential point of the instruction; (4) stressing the importance of the mathematical operation and directing students' attention; (5) commenting and reducing anxiety about the operation; and (6) summarizing and reaching closure. Students reviewing the videotape recognized the instructional techniques of slowing down the pace of instruction, using analogies, repeating, and using gestures. A more detailed analysis of the same videotape and another segment was used to compile information on the frequency of the instructor's various body positions, direction of gaze, gestures, and position in the room. Students interpreted the teacher's use of space as contributing to the learning process and recognized the co-occurring behaviors that signaled a particularly important point. The study supports the findings of other ethnographic research and suggests that the situationally determined and socially negotiated classroom roles can be analyzed in terms of their focal activity. (FG)