We tested whether dreams can anticipate a stressful exam and how failure/success in dreams affect next-day performance. We collected information on students’ dreams during the night preceding the medical school entrance exam. Demographic, academic, sleep and dream characteristics were compared to the students’ grades on the exam. Of the 719 respondents to the questionnaire (of 2324 total students), 60.4% dreamt of the exam during the night preceding it. Problems with the exam appeared in 78% of dreams and primarily involved being late and forgetting answers. Reporting a dream about the exam on the pre-exam night was associated with better performance on the exam (p = .01). The frequency of dreams concerning the exam during the first term predicted proportionally higher performance on the exam (R = 0.1, p = .01). These results suggest that the negative anticipation of a stressful event in dreams is common and that this episodic simulation provides a cognitive gain.