The ability of the CNS to generate seizures as a function of age was investigated utilizing the kindling model of epilepsy. Hourly electrical, low intensity stimulations of the amygdala induced kindling in adult rats, but stimulations delivered at 15 min intervals failed to or markedly retarded the development of kindled convulsions. In contrast, both types of stimulation induced consistent prolongation of the afterdischarges and repeated generalized seizures in suckling rat pups. The rate of development of the kindled convulsions in the pups was similar, irrespective of whether the stimulations were delivered at 15 or 60 min intervals, indicating that short (less than 15 min) seizure refractory periods exist in the immature brain. The data suggest that seizure susceptibility changes with age and is greater early in life.