Recently, there has been growing interest in the association between traumatic brain injury (TBI) and Alzheimer's Disease (AD). TBI and AD share many pathologic features including chronic inflammation and the accumulation of beta amyloid (Aβ). Data from both AD and TBI studies suggest that microglia play a central role in Aβ accumulation after TBI. This paper focuses on the current research on the role of microglia response to Aβ after TBI.