The ability of relatively low doses of atropine, NBQX and TCP administered in combination to prevent or stop seizures induced by soman, was studied in rats. While these drugs injected together early after soman prevented the onset of seizures, their delayed concomitant administration after 5 or 30 min of epileptic activity only mildly attenuated the intensity of seizures. Conversely, a total arrest of epileptic activity was observed in 80 to 100% of animals when NBQX and TCP were given together after 5 to 50 min of seizures to atropine pretreated rats. The large time-window for antiepileptic effectiveness of this 'three drug treatment', provided that atropine is administered early after soman, is discussed in relation to reciprocal potentiations of the antiepileptic effects of atropine, NBQX and TCP in combination.