Seven patients with idiopathic generalized epilepsies were investigated using MEG and EEG. Spike-wave series were seen in all patients, single spikes in six. For both, source analysis showed most often involvement of frontal, perinsular and subcortical/thalamic areas. In all patients, a unilateral frontal accentuation of activity could be observed. Patients with juvenile myoclonic and myoclonic absence epilepsy presented with localizations mainly in the central and premotor regions versus prefrontal accentuation in the other absence patients. MEG/EEG source localization provides important information concerning regional network involvement in idiopathic generalized epilepsies. As a consequence for a neurophysiological concept of "generalized" epileptic seizures and syndromes, a third subgroup with regional activity in bilateral homologous regions can be differentiated next to pure focal and multifocal generalized epilepsies.