Thalamic sites eliciting, facilitating or suppressing attack behavior in cats were explored using implanted electrodes in free-moving animals. In general, the effects are seen following stimulation of the medialis dorsalis and adjacent cell groups. Attack was elicited from the caudal half of nucleus reuniens, the junction of centralis medialis and medialis dorsalis. Hypothalamically-elicited attack was facilitated by stimulation in the dorsal boundary of ventralis anterior with nucleus reticularis, and in the gray just medial to parafascicularis. Suppression of hypothalamically-elicited attack followed stimulation of the dorsolateral junction of ventralis anterior and reticularis, the rostral part of nucleus reuniens and interanteromedialis. Sites were also found in nucleus paratenialis. Some findings on the anatomical projections of some of these areas are presented. The principal new finding was a pathway from anterior nucleus reuniens to the lateral hypothalamus.