Effective stimulation sites for the hypothalamic defensive attach and its related responses were mapped in 65 tame adult cats (107 sites). The hypothalamic defensive attack was classified into two types according to its locomotion component: one with only directed attack and the other with retreat. The retreat appeared accompanied by back arching and intermingled with the directed attack. Otherwise, the directed attack and the retreat were accompanied by the same kinds of threat responses, including piloerection, ear retraction, growling and hissing. Stimulation sites for the directed attack with thresholds under 100 microA were located at the dorsal half of the ventromedial hypothalamic nucleus (VM) and areas just rostral to it. Directed attack with thresholds above 100 microA was elicited by stimulation of the marginal portion of the VM and adjacent areas, especially those rostral to it. Stimulation sites for the directed attack, which was replaced by stereotyped circling at higher intensities, were located at the part of the above-mentioned areas most distant from the VM. The retreat was elicited from the ventral half of the VM. Stimulation sites which evoked stereotyped circling with threat responses were distributed in a wider area of the medial hypothalamic area outside the VM.