Background: Carotid atherosclerosis is a chronic inflammatory disorder and is responsible for the vast majority of ischemic strokes. Inappropriate innate and adaptive immune responses synergize with malfunctional vascular wall cells to cause atherosclerotic lesions. Yet, functional characteristics of specific immune and endothelial cell subsets associated with atherosclerosis and cerebrovascular events are poorly understood. Methods: Here, using single-cell RNA sequencing, the unprecedentedly largest data set from 20 patients' carotid artery plaques and paired peripheral blood mononuclear cells was generated, with which an ultra-high-precision cellular landscape of the atherosclerotic microenvironment involving 372 070 cells was depicted. Results: Compared with peripheral blood mononuclear cells, 3 plaque-specific T-cell subsets exhibiting proatherogenic features of both activation and exhaustion were identified. Strikingly, usually antiatherogenic, CD4+FOXP3+ regulatory T cells from plaques of patients with symptomatic disease acquired proinflammatory properties by probably converting to T helper 17 and T helper 9 cells, while CD4+NR4A1+/C0 and CD8+SLC4A10+ T cells related to cerebrovascular events possessed atherogenic attributes including proinflammation, polarization, and exhaustion. In addition, monocyte-macrophage dynamics dominated innate immune response. Two plaque-specific monocyte subsets performed diametrically opposed functions, EREG+ monocytes promoted cerebrovascular events while C3+ monocytes are anti-inflammatory. Similarly, IGF1+ and HS3ST2+ macrophages with classical proinflammatory M1 macrophage features were annotated and contributed to cerebrovascular events. Moreover, SULF1+ (sulfatase-1) endothelial cells were also found to participate in cerebrovascular events through affecting plaque vulnerability. Conclusions: This compendium of single-cell transcriptome data provides valuable insights into the cellular heterogeneity of the atherosclerotic microenvironment and the development of more precise cardiovascular immunotherapies. Keywords: carotid artery diseases; endothelial cells; immunotherapy; macrophages; monocytes.