Introduction: Medical errors are one of important and noticeable challenges of health care, which threaten the health system of all countries. On the other hands this issue is a global, costly with serious complications for patients and society.

  Objective: The present study aimed to determine the rate of medical adverse events during patients' hospitalization.

  Methods : In this cross sectional study, 390 patients in training hospitals affiliated with Kerman University of Medical Sciences were studied in winter of 2011. Validity and reliability of the patients was determined, using a questionnaire method. Data analysis was carried out using descriptive statistics (mean and standard deviation) and chi square test.

  Results: 50.3% of participants were male. Interpersonal problems happened for 31.8% of patients, medical errors and problems related to treatment process happened for 26.4% and 40% of patients respectively. Total incidence of adverse events for patients was 62.3% during their hospitalization.

  Conclusion: The findings of this study indicated that the incidence of adverse events is common during patient's hospitalization. Therefore, studying medical errors and learning more or how to prevent, monitor and respond to them is essential.