Terrorism is a very complex and ever developing phenomenon, which can be construed as systematic use of organised violence against uninvolved persons for the purpose of achieving political, criminal or other goals. The struggle against it is very complicated, but necessary. Currently, many people especially connect this term with the Islamic religion. Islamic radicals justify the performed terrorist attacks by an extreme perception of the holy book of Quran and proclaim themselves as holy fighters for freedom. However, recent years have shown that terrorism has spread throughout the world and now with the mass migration represents one of the largest threats for today's society. Terrorism develops as fast as our society and prides itself with the ever growing popularity with sponsors of various kinds with different interests, who with their considerable not only financial support allow the terrorist groups to commit more and more sophisticated and destructive attacks. From the perspective of the CR it can be said that our state can fortunately be considered relatively safe, unlike other member countries of the EU. However, it is necessary to take into account the participation of the CR in the international antiterrorist operations, which without question make the CR a potential target of a possible terrorist attack. However, the participation in these missions is necessary. The currently largest terrorist group Islamic State included the Czech Republic in its list of the "crusade coalition" at the end of 2015, where all enemies of this "pseudo-state". The theoretical part of the thesis on the topic of the Development and action of terrorist groups with regard to the situation after 2001 especially deals with the issues of Islamic terrorist groups. In the introduction of the thesis, the fundamental terms of the issues in question, such as terrorism, Islam, jihad, Islamism, Islamic fundamentalism. The second part of the theoretical part of the thesis deals with terrorist organisations. Due to the current safety situation, the main attention was attached to the development and activity of major terrorist groups, that is Hezbollah, Hamas, and of course Al-Qaeda and the Islamic State. These selected terrorist organisations are elucidated in the theses as much as possible, including their leaders. Subsequently, further selected terrorist organisations are linked to these terrorist groups, namely Al-Gama'a al-Islamiyya, Palestine Islamic Jihad, and Taliban. In the initial chapter of the research part of the thesis, a research question is stated, which has been determined as follows: "What is the threat of a terrorist attack in the territory of the Czech Republic?", which directly follows the goal of the thesis, which was stipulated as: "Assessment of the threat of a terrorist attack in the territory of the Czech Republic depending on the development of the terrorist groups." Furthermore, the research methodology is stated. In the following chapter of the research part with the title "Results", the reader first familiarises himself with the largest terrorist attacks so far, which have taken place in the USA, on 11 September 2001 and were a turning point in the history of terrorism. The last pages of this part of the thesis contemplate the attacks of Islamic radicals and the situation in the West after 11 September 2001. The middle part of this chapter familiarises the reader with the threats of terrorism for the CR with an accent on Islamic terrorism. Attention is also paid to the Muslim community living in the CR and EU as a potential risk factor of a possible attack. The last part of this chapter of the thesis states semi-structured interviews, which were conducted with leading experts in the issues of terrorism. In the final chapter with the title "Discussion", an analysis of the examined areas is performed. In the conclusion of the thesis, the research question and the thesis objective are answered.