Worldwide, stroke is the second leading cause of death and a major cause of disability. However, the mortality of stroke differs between countries and geographical regions. In high-income countries, i.e. in the United States, stroke has fallen from the third to the fourth leading cause of death. The risk for ischaemic stroke increases with the degree of internal carotid artery stenosis. 70-99% carotid artery stenosis (according to NASCET) in symptomatic patients is an indication for a vascular intervention since this group will achieve significant benefits from surgical treatment. Asymptomatic patients with 60-99% (according to NASCET) carotid artery stenosis may also benefit from surgical procedures when at least one-factor conditioning a high risk of ischaemic stroke incidence exists. These factors may include morphological structure features of atherosclerotic plaque described in imaging examinations that are indicative of its instability and specific clinical predispositions. The paper presents stages of unstable atherosclerotic plaque development and features of its morphological structure that may significantly increase the risk for ischaemic stroke and compares them with current guidelines: