Master's thesis The criminal offence of murder and aggravated murder in the practice of the Rijeka County Court presents the criminal offence of murder and its qualified form in Croatian criminal legislation and case law. To begin with, the paper contains a historical overview which chronologically follows the ways of punishing the perpetrators and the concept of murder from ancient times to the present day. What follows is a chapter about the criminal offence of murder which first deals with the basic form of that criminal offence, analyzing its legal determinants. After that, the paper deals with attempt and privileged forms of murder. The next chapter covers aggravated murder and it systematically includes all six forms of qualified murder: murder in a cruel or treacherous manner, murder of a person who is especially vulnerable due to his or her age, a severe physical or mental disorder or pregnancy, murder of a family member whom he or she has already abused, murder of another out of greed, ruthless revenge, hatred or other base motives, murder of another in order to commit or cover up another criminal offence and murder of an official person in relation to his or her performance of official duties. The paper also shows statistical data concerning criminal offence of murder and aggravated murder. Finally, the paper reports on the results of a legal study conducted in the Rijeka County Court. It includes an analysis of the case law of that court concerning murder and aggravated murder. In those cases the final judgments are rendered in the time period from January 1st 2017. to December 31st 2021.