The second preclinical year of the medical curriculum at the Medical Faculty of the University of Lausanne in Switzerland includes nine multidisciplinary organ-system-oriented modules consisting of lectures and problem-based-learning tutorials. This study reports the experience accumulated with the evaluation of lectures during the academic years 1998-1999 and 1999-2000. The ratings of the different modules were highly variable, indicating the ability of students to have a critical view on the teaching and the teachers. There was a close to very close correlation between the ratings obtained during the two study years. The high discriminative capacity of students in evaluating the teaching and the teachers was also supported by their critical point of view expressed in free comments. Our observations stress therefore the reliability of teaching evaluations systematically performed by medical students. (Contains 5 tables and 1 figure.)