An acute trauma to the CNS rapidly results in the upregulation of inflammatory cytokines that include interleukin‐1 (IL‐1). We report here that the levels of several matrix metalloproteinases (MMPs) are also elevated following a corticectomy trauma injury to the mouse CNS. The delayed upregulation of MMPs compared to that for IL‐1 suggests the possibility that inflammatory cytokines regulate MMP production in CNS trauma. To resolve this, we developed a method to isolate and maintain highly enriched human fetal neurons or astrocytes in culture and examined the regulation by cytokines of the activity of a subgroup of MMPs, the gelatinases (MMP‐2 and ‐9). While both neuronal and astrocytic cultures displayed comparable MMP‐2 activity, as evidenced by gelatin zymography, levels of MMP‐9 were proportionately higher in neurons compared to astrocytes. Of a variety of cytokines and growth factors tested in vitro, only IL‐1β was effective in increasing the neuronal expression of MMP‐9. Finally, an IL‐1 receptor antagonist attenuated the increase of neuronal MMP‐9 in culture and abolished the injury‐induced increase of MMP‐9 in the mouse brain. These results implicate IL‐1β as a key regulator of neuronal MMP‐9 in culture and of the elevation of MMP‐9 that occurs following mouse CNS trauma. J. Neurosci. Res. 61:212–224, 2000. © 2000 Wiley‐Liss, Inc.