Introduction. The comprehensive basic science exam is the most important exam for medical students which can assess their capabilities in mastering general medicine. The experience has shown that the unsuccessful students face difficulties during later periods. This survey aims to determine the role of educational and demographic factors in basic sciences examination results. Methods. All the students who took the comprehensive exam (73 persons) participated in this descriptive-analytical study. In order to get the related factors, the score of the basic sciences courses, the result of the final basic sciences examination and the students’ demographic characteristics were obtained from their files. These data were ananlyzed by SPSS software and the Relative Risk of failing in comprehensive exam was determined.Results. Twenty students out of 73 failed the examination. The Relative Risk (RR) of failing in the final basic sciences examination for those who obtained bad mark in Histology, Immunology and Health 3 were 10.32, 4.55 and 4.11, respectively and were significant. The Relative Risk of failing for dormitory residents, students selected through Quota system and those who finished basic sciences in more than 5 semesters were 7.2, 3.4 and 3.1, respectively and were significant. Regression model showed that the important independent variables which correlated to our response variable were Embryology, Psychology, Physiology2, Histology and Microbiology.Conclusion. The variables such as quota system selection, the period of basic sciences, and residency in university dormitory have important roles in the results of basic sciences examination. The courses of Physiology 2, Microbiology, Histology and the variable of quota system selection, due to having large and significance Relative Risk, are the most important variables correlated to the score and result of the comprehensive exam.