Cerebral amyloid angiopathy (CAA) is a disorder characterized by the deposition of amyloid in the leptomeningeal and cortical blood vessels. Sporadic amyloid β (Aβ)-type CAA is the most common form of CAA. Although CAA is a well-known cause for recurrent cerebral lobar hemorrhage, inflammation, and vasculitis, CAA-related inflammation/vasculitis (CAA-ri/vasculitis) induced by Aβ deposition on vessel walls is emerging as a treatable condition. The estimated total number of cases of and prevalence of CAA-ri/vasculitis in Japan were 170 and 0.13 per 100 000 population, respectively. Patients with CAA-ri/vasculitis show acute or subacute-onset of cognitive impairment, behavioral changes, and headache. Brain magnetic resonance imaging, showing asymmetrical white matter abnormalities and occasional meningeal enhancement, is a useful tool for the diagnosis of CAA-ri/vasculitis. Moreover, elevation of anti-Aβ antibodies and inflammatory markers in the cerebrospinal fluid can help in clinical diagnosis. Although several clinical diagnostic criteria have been proposed, neuropathological examination of a brain biopsy remains the gold standard for detecting severe Aβ deposition and vasculopathic changes with lymphocytic infiltrations and/or granulomatous vasculitis. No validated treatment regimen has been established to date. Nearly 80% patients with CAA-ri/vasculitis improved after immunosuppressant therapy with corticosteroid and/or cyclophosphamide. Early treatment is essential to prevent irreversible sequelae in the brain.