We studied the local phase shifts in rats ECoG at the rest and spike-wave activity during epileptic seizures induced by applique 4-Aminopyridine on the cortex during chronic experiments. Rats were implanted by two cannula and 8 needle electrodes in the somatosensory cortex of two parallel rows (4) in the left and right hemisphere. We measured the amplitude of spontaneous waves ECoG in the background and spike-wave activity complexes while seizure, as well as the phase shifts between adjacent points of the resulting rectangular grid in the same conditions. The background showed the motion of ECoG waves towards to reducing their amplitude. The same is true for epileptic activity when seizure initiating. The maximum amplitude and the earliest phase were recorded in the point of drug application. During generalization of saizure the increases of epileptic complexes amplitude was accompanied with decrease of frequency. So the local phase shifts reduced and their relationship with the amplitude decreased or disappeared. At the maximum development of seizure activity was observed the simultaneous beginning of the spike-wave complexes at all points.