The ability of NBQX, a potent antagonist of AMPA glutamatergic receptors, to prevent or stop seizures induced by the organophosphate soman, an irreversible inhibitor of AChE, was studied in rats. NBQX administered concomitantly with soman prevents the onset of seizures (ED50: 29.2 mg kg−1, i.p.). Administered 5 min after the onset of seizures, NBQX greatly reduces the intensity of the epileptic activity. The same decrease of epileptic activity is observed, in the presence of atropine, when the administration of NBQX is delayed 15 min after the onset of seizures. NBQX thus appears as a promising antiepileptic candidate against soman-induced seizures. The roles of AMPA and muscarinic receptors in the onset and propagation of soman-induced epileptic activity are discussed.