Objectives and background: The primary objective of this research is to compare the total population mortality rates in the Split-Dalmatia County in the weeks before and after one hour shift during spring and autumn transition of daylight saving time in the period from 2011. to 2015. The secondary goal is to compare the results with other surveys in the world and to see the significance of daylight saving time transitions on population mortality. Patients and method: The participants in research were all deceased people in the Split-Dalmatia County area a week before and a week after the spring and autumn transition of daylight saving time. A total of 898 person were analyzed in the studies. The following data regarding the participants were analysed: date of birth, sex, date of death, cause of death and week of death in daylight saving time period. Results: By comparing the overall mortality rate a week before and after the autumn and spring transition of daylight saving time, we revealed a significant increase in mortality in the week after transition (p = 0.05). In the spring transition of daylight saving time we found a significant increase in mortalitycaused by natural causes in the week following the transition (p = 0.03), while that could not be concluded for violent deaths. In the autumn transition period of daylight saving time we did not find a significant increase in mortality caused by natural and violent causes of death in the week following the transition. For the mortality of myocardial infarction, cerebrovascular insult and malignant diseases, we did not find a significant increase in the week after the transition, as well as for violent deaths (murders, suicides, and traffic accidents). Conclusion: According to the above, the transitions of daylight saving time could be dangerous to human health and increase overall mortality, especially when it comes to natural death during the spring transition. The exact mechanism of disturbance of circadian rhythm during the transitions of daylight savings and effects on human health is not known and further research is needed.