This chapter considers the potential mechanisms by which cerebral microbleeds (CMBs) could cause or be associated with neurological dysfunction. It then focuses on CMBs in relation to transient neurological symptoms (mainly in the context of cerebral amyloid angiopathy [CAA]) and briefly discusses their association with disability and mortality. A fundamental challenge in studying how CMBs could affect brain function is that they are closely linked to many clinical and imaging manifestations of cerebrovascular disease, including all types of ischemic stroke and intracerebral hemorrhage (ICH). In patients with transient neurological symptoms related to CAA, a seizure-like mechanism may be particularly likely when the symptoms are stereotypical, spread to contiguous cortical regions or resolve with anticonvulsant drugs. The accumulation of CMBs might reflect progressive small vessel pathology and so could result in the development of progressive disability or even be associated with an increased risk of death.