Abstract Development of seizures in response to repeated amygdaloid electrical stimulation (kindling) was assessed under conditions of diazepam (3 mg/kg), phenobarbital (40 mg/kg), and diphenylhydantoin (20 mg/kg). Daily 1-sec trains of biphasic square-wave pulses elicited afterdischarge under all conditions and produced full motor seizures in a median of 9 days in control and 8 days in diphenylhydantoin conditions. The same stimulation produced afterdischarge but did not produce seizures after 14 days of stimulation in diazepam and phenobarbital conditions. No savings were found when the diazepam and phenobarbital animals were subsequently stimulated to full seizure in the nondrugged condition. Afterdischarge thresholds were unaffected by diazepam but were doubled by phenobarbital. Motor seizure could not be evoked under diazepam or phenobarbital even in animals fully kindled prior to drug testing, and even when stimulation intensity was raised from the normally effective 250 μa to a maximum of 5 ma. Neither diazepam nor phenobarbital interfered with the decrease in local afterdischarge threshold which was produced by repeated stimulation, but both drugs attenuated propagation of afterdischarge to the contralateral amygdala. The ineffectiveness of diphenylhydantoin may have been due to inadequate dosage or may have reflected the relative ineffectiveness of this drug with clonic seizures.