The pilocarpine model of epilepsy in rats is characterised by the occurrence of spontaneous seizures (SRSs) during the chronic period that recur 2-3 times per week during the whole animal life. In a previous study on brain metabolism during the chronic period of the pilocarpine model it was possible to observe that, among several brain structures, the lateral posterior thalamic nuclei (LP) showed a strikingly increased metabolism. Some evidences suggest that the LP can participate in an inhibitory control system involved in the propagation of the seizures. The aim of the present study was to verify the role of LP in the expression and frequency of spontaneous seizures observed in the pilocarpine model. Ten adult male rats presenting SRSs were monitored for behavioural events by video system one month before and one month after LP ibotenic acid lesion. Another group of chronic epileptic rats (n=10) had the anteroventral thalamic nuclei (AV) lesioned by ibotenic acid. After the surgical procedure, the animals were sacrified and the brains were processed for histological analysis by the Nissl method. The LP group seizure frequency was 3.1+/-1.9 before ibotenic acid injection and showed an increase (16.3+/-7.2 per week) after LP lesion. No changes in SRSs frequency were observed in the AV group after ibotenic lesion in these nuclei. These results seem to suggest that LP play a role in the seizure circuitry inhibiting the expression of spontaneous seizures in the pilocarpine model.