Admissions tests are an integral part of conference interpreter education, yet little is known about their effectiveness and efficiency. The authors discuss general principles of admissions testing, focusing specifically on predictive validity and on measuring aptitude, the main component of interpreter training program admissions tests. They describe the underpinning of developing admissions tests with high predictive validity of end-of-course exam performance. The authors then evaluate and report the efficiency of an existing aptitude test by looking at historical records of admissions testing results and end-of-course exam results in one interpreting school. Multiple linear and logistic regression analyses indicate that these tests are poor predictors of students’ success rate. Future research should focus on developing tests with better predictive validity assessed on empirical grounds.