Background & Aim: Sleep disorder is associated with considerable problems in educational, vocational and social performance. This study was performed to assess the prevalence of sleep disorders among medical students of Yasuj university of Medical sciences in 2014.

Material & Methods: This cross–sectional descriptive study was performed on 151 medical students of yasuj university of medical sciences who were selected by available sampling. For data collection, a two-part questionnaire was used, the first part was demographic information and the second part was Pittsburgh Sleep Quality Questionnaire. The data were analyzed by SPSS 21 software, using T-test, Chi-square, and descriptive test.

Results:  the results showed that sleep duration of medical students was 5.9±0.7 hours and 69.95% of medical students had poor sleep quality. There were negative significant relationship between sleep duration and age (p=0.01) and academic level (p=0.026), as sleep duration decreased with increasing the age and academic level especially in clinical courses. Interns had the shortest sleep duration among medical students, the effective sleep duration in majority of medical students was less than 7 hours.

Conclusion: The results showed that the majority of students had poor sleep quality .Since a large percentage of students suffer from sleep disorders, It is hoped be determined programs to assess and diagnose sleep disorders.