Microglia and astrocytes produce several cytokines including interleukin 1 (IL1) and tumor necrosis factor alpha (TNF alpha), which have pleiotropic effects in the immune and nervous systems. Recent evidence has come to light that they play a role in damage in the central nervous system. This indeed may be the result of overproduction of these factors as the consequence of trauma or disease. At lower concentrations, however, they may in fact be involved in the normal development of the nervous system. A review of brain IL1 and TNF alpha during normal development, abnormal development, and pathology is presented here. We have speculated as to the association of these cytokines directly and indirectly with neural cell migration, proliferation, differentiation, and death.