Due to largely considerable role of basic sciences curriculum as a primary phase on academic education, facing challenges during education may have adverse impacts on their future medical education or their professional career. In addition, a curriculum evaluation based on long term periods may provide a better and broader vision for educational planning. In current cohort study, all of medical students from Semnan University of Medical Sciences enrolled in comprehensive basic science exam during 2001-2010 were randomly selected. Data collection was permitted and approved by the institutional review board of medical faculty and processed descriptively. The participants of this study consisted of 316 students; the highest (32) and the least (3) amount of members enrolled in pre-internship exams were related to Feb 2001 and Feb 2009, respectively. The highest educational score average was 145 that obtained in Feb 2001 and the lowest educational score average e was calculated 100 and obtained in Feb 2009; furthermore, that group whose educational scores related to February exam with a mean score of 128.8 revealed better educational performances in comparison to September exam groups with a mean score of 114.2; scores obtained in the first-five-year period with a mean score of 125.7 indicated better educational performance when it compared to the second-five-year period with a mean score of 117.1. While the highest educational performance was observed in pathology, microbiology, physiology, and immunology courses, the lowest educational performance were obtained in biophysics, embryology and public health courses. Hence, further research seems required to have a better understanding of the underlying factors in educational performance and thus institutional research is recommended to conduct long term assessment of educational performance.