Cerebral amyloid angiopathy (CAA) is a disorder characterized by the deposition of amyloid β (Aβ) in the walls of small cortical and leptomeningeal arteries, leading to intracerebral hemorrhage (ICH). Definitive diagnosis requires autopsy, but the Boston Criteria, developed in 1995 and 1996, provide a standardized method for ante-mortem diagnosis. These criteria use clinical, radiologic, and pathologic data to classify lobar ICH into possible, probable, or definite CAA. They are crucial for future clinical studies. CAA is a major cause of ICH in the elderly, often associated with dementia and increased risk of anticoagulant-related ICH. The pathogenesis involves Aβ deposition in arterial walls, leading to vessel fragility and hemorrhage. CAA and Alzheimer's disease often co-exist, with shared risk factors like age and apolipoprotein E genotype. CAA-related ICH is most common in elderly patients with lobar ICH, distinct from deep brain hemorrhages. CAA is more prevalent in older adults, with higher rates in those over 70 and 90 years. While ICH occurs in a minority of CAA cases, vascular amyloid deposition may cause symptoms through brain ischemia or cognitive impairment. CAA is associated with increased risk of recurrent ICH, particularly in patients with the ε2 or ε4 apolipoprotein E alleles. CAA-related ICH is often in frontal or parietal regions, and may occasionally occur in non-lobar areas like the cerebellum. Mortality ranges from 10% to 40%, with factors like age, consciousness, and hematoma volume influencing prognosis. CAA can cause clinical syndromes beyond ICH, including transient neurologic symptoms, small cortical infarctions, dementia, and leukoencephalopathy. Definitive diagnosis requires microscopic examination of brain tissue showing hyaline eosinophilic material consistent with Aβ, confirmed by Congo red staining and immunohistochemistry. Autopsy remains the gold standard for diagnosis.Cerebral amyloid angiopathy (CAA) is a disorder characterized by the deposition of amyloid β (Aβ) in the walls of small cortical and leptomeningeal arteries, leading to intracerebral hemorrhage (ICH). Definitive diagnosis requires autopsy, but the Boston Criteria, developed in 1995 and 1996, provide a standardized method for ante-mortem diagnosis. These criteria use clinical, radiologic, and pathologic data to classify lobar ICH into possible, probable, or definite CAA. They are crucial for future clinical studies. CAA is a major cause of ICH in the elderly, often associated with dementia and increased risk of anticoagulant-related ICH. The pathogenesis involves Aβ deposition in arterial walls, leading to vessel fragility and hemorrhage. CAA and Alzheimer's disease often co-exist, with shared risk factors like age and apolipoprotein E genotype. CAA-related ICH is most common in elderly patients with lobar ICH, distinct from deep brain hemorrhages. CAA is more prevalent in older adults, with higher rates in those over 70 and 90 years. While ICH occurs in a minority of CAA cases, vascular amyloid deposition may cause symptoms through brain ischemia or cognitive impairment. CAA is associated with increased risk of recurrent ICH, particularly in patients with the ε2 or ε4 apolipoprotein E alleles. CAA-related ICH is often in frontal or parietal regions, and may occasionally occur in non-lobar areas like the cerebellum. Mortality ranges from 10% to 40%, with factors like age, consciousness, and hematoma volume influencing prognosis. CAA can cause clinical syndromes beyond ICH, including transient neurologic symptoms, small cortical infarctions, dementia, and leukoencephalopathy. Definitive diagnosis requires microscopic examination of brain tissue showing hyaline eosinophilic material consistent with Aβ, confirmed by Congo red staining and immunohistochemistry. Autopsy remains the gold standard for diagnosis.