Educational institutions use different ways to evaluate their teachers. Asking students to rate their teachers is common practice. The purpose of this research was to examine the reliability of the instruments used to evaluate the instructors in a college of medicine. This cross-sectional descriptive research used questioners that evaluated instructors. The questioner was targeting different dimensions of instructors. Item analysis in addition to exploratory factor analysis was performed on 1040questioners answered by the students of the College of Medicine of Kashan University of Medical Sciences. SPSS software was used to perform the analysis. The psychometric properties of questionnaires including Cronbach alpha was determined. The result of exploratory factor analysis and item analysis indicated that three of the subscales of the questioner showed sufficient reliability to evaluate the instructors and two subscales needed further examination. This type of evaluations is necessary to ensure quality of instructors working in an institution as well as providing reliable feedback to the instructors. The result showed that while some subscales of the questioner seems to target the concept of interest; a re-evaluation of the instrument would be valuable to increase its reliability for the administrators in the colleges.