A study was conducted to identify teacher behaviors that college students deem unethical, measure the strength of student attitudes toward the 20 most frequently mentioned behaviors, and measure the degree to which the students have personally found the 20 behaviors to be problems. The first part of the study elicited examples of unethical teacher behavior from 65 students in three communication courses. The 20 most frequently mentioned behaviors were used to construct a questionnaire administered to 155 students at the same college in the summer of 1982. The behaviors that were most unethical and that created the most problems were showing lack of care about students and their concerns; showing favoritism in grading; giving students an unreasonable amount of work; and showing prejudice against students because of race, sex, religion, attire, or major. Least unethical and causing the fewest problems were presenting material with little or no relationship to the course, adding unannounced assignments during the semester, using offensive language in class, and giving unannounced quizzes. (The actual research instrument is included in the text.) (JL)