Subconvulsive doses (25 mg/kg) of pentylenetetrazol were administered at intervals of 4 days for 20 sessions, to induce kindling in conscious, free-moving rats, with chronically-implanted electrodes. This regimen induced an excitation of the CNS, which intensified over the 20 sessions. Periods of motor arrest, concurrent with bursts of electrocortical spike-wave activity, increased to clonic convulsions, concurrent with bursts of spike activity. Separate groups of rats were pretreated over the twenty sessions with nonsteroidal anti-inflammatory drugs (NSAIDs). Pretreatment with paracetamol produced a dose-related reduction in pentylenetetrazol-induced seizure activity. Pretreatment with 20 mg/kg mefenamic acid attenuated, while 60 mg/kg dose potentiated, the pentylenetetrazol-induced excitation. Pretreatment with 10 or 30 mg/kg ibuprofen had no significant effect, while 90 mg/kg was lethal, by itself, in 58% of the group. When all the groups received a single dose of pentylenetetrazol, three weeks after the twenty sessions, there were no significant differences between the groups in level of pentylenetetrazol-induced excitation, when compared to the control (saline-pretreated) group. This suggests that the effective NSAIDs had influenced the manifestation of, but not development of, epileptogenesis over the 20 sessions.