Lyme disease has been associated with damaging inflammation within the central nervous system. In the present study, we demonstrate that Borrelia burgdorferi is a significant stimulus for the production of IL-6, TNF-alpha, and PGE(2) by microglia. This effect is associated with induction of NF-kappaB, and increased expression of Toll-like receptor 2 and CD14, receptors known to underlie spirochete activation of other immune cell types. These studies identify microglia as a previously unappreciated source of inflammatory mediator production following challenge with B. burgdorferi. Such production may play an important role during the development of Lyme neuroborreliosis.