The inhibitory effects of ceruletide (CLT), a cholecystokinin-8 (CCK)-like peptide, were investigated in the epileptogenesis in the amygdaloid kindled rats. Lower doses of CLT (20-80 micrograms/kg) inhibited the progression of kindling process. After acquiring C5 stage, a higher dose (160 micrograms/kg) was required to suppress the seizure susceptibility. These results, in light of several previous studies showing no serious side effects, suggest that CLT might be useful as an anti-epileptogenic agent for clinical usage.