Idiopathic generalized epilepsy is characterized by the spontaneous occurrence on the electroencephalogram of bilateral synchronous spike and wave discharges that involve the entire cortical mantle from the very onset. A central role in cortical synchronization is played by the thalamus, and in particular by the reticularis thalami nucleus, which is regarded as the pacemaker structure for the rhythmic cortical oscillations called spindle activity. Several studies have suggested that the network mechanisms which underlie spindle generation can also account for spike and wave discharges. Experimental investigations on genetic animal models of generalized epilepsy, in which seizures occur spontaneously in the absence of any inductive agent, confirmed that the thalamo-cortical system is involved in spike and wave discharge generation. According to these studies a genetically determined dysfunction in reticularis thalami neurons may alter the electroresponsiveness of the developing thalamo cortical system and cause a persistent state of abnormal excitation.