Background: This study aims to assess stress level and its drivers among medical students using a PBL teaching system Method: Higher Education Stress Inventory (HESI,) was used to assess stress among medical students. All students in the College of Medicine were enrolled. Results: The response rate was 99%.The prevalence of stress was 54.7%. The overall mean stress score was higher in the 4th year students (2.64) than 1st year students (2.52) (p = 0.01). Junior students were more likely to be stressed by lack of clarity of the aims of the study (p = 0.014) and lack of feedback from the teachers (p = 0.003). Senior students were more likely to be stressed by lack of time for other activities (p = 0.036), financial worries (p = 0.027) and about preparedness for future profession (p = 0.007) Despite the high stress scores, only 8.3% regretted their choice of career and 9.3% felt that they are not prepared well for their future profession Conclusions: High level of stress was noted especially among senior students. Stress in junior students was more likely to be medical training-related and to be personal problems-related in senior students. The vast majority of students were happy with their choice of profession and optimistic about their future.