We investigated the effects of chemical convulsants in the leopard frog. Systemic kainic acid (5-20 mg/kg) caused limbic-like seizures, with staring, catatonia, fasciculations, and severe motor seizures, which were almost always lethal. Intracerebral electroencephalographic (EEG) recordings showed spike or spike-and-wave patterns at 6-8 Hz that decreased in frequency and increased in amplitude, maximal at an electrode in the midline olfactory/telencephalic (OLF-M) region. With time, an interictal pattern of 100-200 microV periodic spikes developed, followed by diffuse suppression of all brain activity. Seizures induced by pentylenetetrazole (150-450 mg/kg) and bicuculline (5-10 mg/kg) were characterized by the abrupt onset of motor activity, which continued intermittently for several hours, followed by recovery. EEG recordings in animals treated with pentylenetetrazole showed rhythmic spike-and-wave bursts at 1.5-3 Hz that were maximal at OLF-M. Recordings from frogs treated with bicuculline showed repetitive 3-6 Hz spike-and-wave discharges maximal at OLF-M that were nearly constant in amplitude and at times became continuous. Strychnine (1-5 mg/kg) caused reversible seizures characterized by tonic extensions of the extremities, that seemed to originate in the spinal cord. Frogs with recurrent seizures from systemic cis-diamminedichloroplatinum II showed 4-8 Hz rhythmic spike-and-wave activity that gradually slowed in frequency and increased in amplitude. Thus, the frog's reactivity to convulsive agents is similar to that of mammals.