Background: Determining the cause of death is one of the most important diagnoses issued by physicians and lack of enough precision and failure to observe scientific principles can lead to serious legal problems for physicians. Death can be accrued in two forms; apparent death and  definitive, Lack of attention to the possibility of apparent death in the diagnosis of death, in addition to causing delay in CPR proceedings, can lead to complaints by patient's relatives, which make physicians face serious problems. This study was carried out to examine the cause of death determined after autopsy in dissection hall of Tehran Legal Medicine Center and compare it with the cause of death determined in treatment centers during 2012.

Methods: A retrospective cross-sectional study was designed with two data collection tools: the first consisted of clinical information available in 4641 death files referred from health centers to Tehran Legal Medicine Center in order to determine the cause of death; the second part related to autopsy findings (both pathology and serology) and definite cause of death. Data were analyzed by statistical software SPSS version 13. Chi-square and kapa conformation were used for nomination of concurrence between forensic reports and other report.

Findings: The highest percentage of non-identical cause of death is related to internal medicine specialists with 47.40 % and the lowest percentage is related to neurosurgery specialists with 1.85%.

Conclusion: Considering the low rate of correct clinical diagnosis of cause of death in this study, post-mortem examination remains a valuable source of pertinent information. Based on the results we suggest that considering the high rate of mistakes in determining the cause of death by doctors, they should be informed of the results of autopsy and determination of the final cause of death of their patients in order to have more accurate clinical diagnosis when facing with similar cases.