Introduction: Today, development of professionalism is acritical aim of medical schools. Studies have demonstrated thatmedical students’ perceived level of professionalism is inadequateworldwide. This study aimed to investigate the medical students’perceptions of their colleagues’ professional behavior.Methods: This study is a cross-sectional study with 280 medicalstudents at Shiraz University of Medical Sciences in their fifthto seventh year of study as the sample. The study was performedduring one month in 2013, using stratified random samplingmethod. The instrument of the study was the Persian version ofthe questionnaire of the American Board of Internal Medicine(ABIM).The questionnaire includes demographic information,questions about the meaning of the professionalism, history ofmedical ethics education programs and 12 behavioral questions.The data were analyzed using student t-test and Pearson correlationtest. The significance level was set as 0.05.Results: Forty percent of respondents did not know the meaning ofprofessionalism. The mean±SD score of behavioral questions was5.91±1.2 on a scale from 0 to 10. The mean±SD score of excellencequestions was 4.94±1.7. It was 7.05±1.9 for ‘honor/integrity’, and6.07±2.1 for ‘altruism/respect’ questions. There was a significantassociation between gender and excellence score (p=0.007).Conclusion: Medical students assessed their colleagues’professional behavior as poor. They did not have properinformation about professionalism. Medical students are futuregeneral practitioners and respecting medical ethics by them is veryimportant in a perfect health system. Universities should emphasizethe importance of teaching professionalism to medical studentsand faculty members, using innovative education methods.Keywords: Professionalism; Excellence; Respect; Medical students