The purpose of this study was to determine if a male physical educator's appearance of body fatness affects his ability to teach and instill good exercise intentions in high school students. Eight hundred and fifty students viewed one of two 20-minute videotapes in which exercise concepts were presented. The tapes were identical except that in one of the tapes the instructor's body dimensions were altered by a "fat" suit. Immediately upon seeing the tape, the students completed a content examination and questionnaire. Viewers of the overweight instructor's tape scored lower on all aspects of the examination, exhibited a lesser intent to exercise, and less favorably rated the teacher's likability, expertise, and appropriateness as a role model. It was concluded that a male physical educator's appearance may be a very powerful variable mediating teacher effectiveness. A table and six figures detailing student responses are appended. (MT)