Background and purpose: Data in death certificates acts as a basis in epidemiological studies. Community health statistics broadly originates from necrology, therefore, underlying cause of death is highly important. The aim of this research was to determine the extent of ambiguous symptoms, signs, and causes in mortality certificates.

Materials and methods: A retrospective descriptive analysis was conducted in which mortality certificates issued by hospitals affiliated with Mazandaran University of Medical Sciences in 2010-2014 (n= 20233) were investigated. A checklist was used to collect the information. Data was then analyzed in SPSS V.18. Chi-square test was applied to determine the significance of relationship.

Results: Twenty three percent of death certificates reported ambiguous symptoms and causes as the cause of death. Vague and poorly defined causes were more common in private hospitals (33.7%) and in those older than 60 years of age (51%). Based on the findings, the less patients stayed in hospital, the more unclear causes were recorded.

Conclusion: Ambiguous symptoms and causes are the second cause of death on death certificates. Such data is worthless in health planning, therefore, it is essential to take measures for training the doctors and launching a smart system of mortality registration.