This paper measures the impact of timing on student evaluations of teaching effectiveness, using a dataset of close to 3000 observations from Erasmus School of Economics. A special feature of the data is that students were able to complete on-line questionnaires during a time window ranging from one week "before" to one week "after" the final examination. This allows for the isolation of the effect of the examination on student evaluations. Among students who subsequently pass the exam, we find little difference between pre- and post-exam ratings. Among students who fail, evaluation scores are significantly lower after the exam on a number of items. Our evidence is compatible with a self-serving bias in student evaluations, but does not indicate that students seek revenge on instructors through lower ratings. (Contains 6 tables.)