Concurrent monitorings of polygraph and continuous measurements of rCBF of the epileptic focus were made in the nonanesthetized chronic cats. The influences of the sleep-wakefulness cycle on IIDs and rCBF of the epileptic focus of the hippocampus were analyzed. 1) IIDs increased remarkably during LSW and DSW but not as much as during DSW-P. 2) The rCBF decreased gradually during LSW and DSW. But the rCBF during DSW-P increased slightly as compared to that of DSW. 3) The frequencies of IIDs increased in association with hypoperfusion of the epileptic focus. 4) The spiking rate of the hippocampal focus decreased with the appearance of PGO during the deep slow wave sleep stages.