The thalamus of unanesthetized unrestrained cats was explored stereotaxically for sites which when electrically stimulated will either give rise to attack, facilitate attack elicited from the hypothalamus, or suppress such attack. A quiet biting form of attack could be elicited from the medial portion of nucleus dorsalis medialis, the caudal portion of nucleus reuniens, the midline region of nucleus centralis medialis, and anterolateral portions of nucleus reticularis. Facilitation of hypothalamic attack also occurred with stimulation of these same sites. In addition, facilitation was observed from sites that did not give rise to attack. These include nucleus ventralis anterior, area subparafascicularis, and the paraventricular region medial to the nucleus parafascicularis. Suppression of attack was elicited by stimulation of sites which by themselves gave rise to retreat from discrete objects in the environment, or to "fear-like" responses. The areas whose excitation suppressed attack include anterolateral portion of the reticular nucleus, the region of the anterior thalamic radiations, the rostral portion of nucleus reuniens, nucleus interoanteromedialis, somewhat lateral portions of nucleus dorsalis medialis and posterior portions of centrum medianum. The responses seen by a number of previous investigators are also confirmed. Finally, the possible pathways mediating attack and its suppression are discussed.