We examined the effects of professor reputation versus first impressions on student evaluations of instruction. Students in 19 Psychology courses completed course evaluation surveys either before meeting the instructor or 2 weeks into the semester. Both groups then completed the course evaluation again at the end of the semester. Unlike evaluations completed prior to meeting the professor, students' ratings 2 weeks into the semester did not differ from end-of-semester evaluations. Therefore, students considered first impressions more important than professor reputation as determinants of their end-of-the semester evaluations. Results suggest that students form lasting impressions within the first 2 weeks of classes.