In this qualitative study, the factors affecting the first rank in epidemiology course earned by medical students of Kurdistan University of Medical Sciences in pre-internship exams of March, 2009 and September, 2010 was investigated. A total of 43 students who had participated in the given exams were selected through census sampling technique. Two epidemiology teachers were also selected using a purposive sampling technique. Students' data were gathered through a questionnaire. Teachers' data were collected using a semi-structured interview method. From the 43 administered questionnaires, 30 questionnaires were returned. The themes associated with the students were the teachers’ expertise, appropriate syllabus, proper teaching methods and students’ motivation and the themes related to the teachers were expertise and a defined curriculum. The findings of this study showed that appropriate curriculum and teachers’ expertise were the factors that exerted a great impact on obtaining a first rank by students in pre-internship exam.