Objective: To define variants of the Willi’s circle and also structural features of the vessel walls at the site of aneurysm location in people who died from ruptured aneurysm to identify risk groups for cerebrovascular disease. Material and methods: The structure of cerebral vessels of 12 people at the age from 17 to 69 of both sexes who died from subarachnoid hemorrhage of aneurysmal genesis was examined due to macro-microscopical and clinical methods. Histology slides of cerebral arterial walls of aneurysm area were stained with hematoxylin-eosin and Mallory’s technique and then were examined. Results: Variants of the Willi’s circle and morphological features of vessel walls located in aneurysm formation area in people who died from aneurysm rupture are shown in the article. Conclusion: Not classic variants of Willi’s circle, fibromuscular dysplasia of the medial type and atherosclerotic changes of vessel walls contribute to aneurysm occurrence in cerebral vessels.