Electroencephalographic activity and behaviors were recorded in unrestrained adult rats during their first meal and intermeal interval following 17 hrs of food deprivation. Cholecystokinin (CCK-8), in doses of 5, 10, 20, 40, and 80 IDU/kg injected intraperitoneally 10 min after feeding began, suppressed ingestion, elicited and prolonged rest behavior, synchronous wave sleep, and desynchronous wave sleep in a dose-related manner. The 80 IDU/kg dose elicited EEG and behavioral patterns indistinguishable from those of the postprandial control rats. The results suggest that cholecystokinin elicits satiety for food in rats, not illness. The results also suggest that EEG measures can be used to quantify the postprandial state of satiety.