Matrix metalloproteinases (MMPs) are important in various pathophysiological processes related with the tissue remodeling. We planned the experiments to determine whether MMPs participate in disruption and repair of the tissue following brain injury. We have studied induction of MMP-9, a 92 kilodalton (kDa) gelatinase, in traumatic brain tissue, which may be produced by brain residual cells. We speculate that MMP-9 plays a role in post-traumatic brain edema formation.