Prior high school educational attainment and medical aptitude tests are two of the most frequently used selection procedures for admission to medical school. Both of these have been shown to correlate with future performance. However, there is a need for further analysis of the combined impact of these two admissions tools and comparison of their predictive value for future performance. At present, successful completion of high school (Matura) and an aptitude test (Eignungstest Medizinstudium Schweiz, EMS; Swiss Aptitude Test in Medicine) are used for admission to all medical schools in the German-speaking part of Switzerland. The purpose of this study was to explore the predictors that are most decisive for performance in undergraduate medical education. More precisely, we were interested in the contributions of the Matura grade and the EMS score to explanations of performance in the Bachelor program of Medicine at the University of Bern. Matura grades, EMS score and performance in the Bachelor program of Medicine were collected for 730 students from four cohorts. Of these, 277 graduated from high school with a biology-chemistry major. Hierarchical regression analysis was conducted for each study year and type of examination to determine which predictors affected performance during undergraduate medical education. These data show that Matura grades are an important predictor for performance in undergraduate medical education. The EMS score had no impact when the Matura grades were part of the analysis. The biology-chemistry major grade was a predictor for performance in the first year of undergraduate study. From the second academic year onwards, past performance in the bachelor’s program was the best predictor for future performance during undergraduate medical education. Students’ Matura grades predicted their subsequent performance in undergraduate medical education in the bachelor’s program of the University of Bern. In contrast, EMS scores do not explain any additional variance in students’ performance throughout the entire bachelor’s program. These findings suggest a need for rethinking the admission process.