Abstract Attack was elicited in normally non-aggressive rats by electrical stimulation of 53 points in the ventrolateral hypothalamus. Attack specificity tests disclosed that live mice, dead mice, and juvenile rat pups were attacked with significantly greater frequency, shorter latency, and longer duration than adult rats of either sex or guinea pigs, and that attacks on live mice were more persistent than on dead mice. There was no evidence for olfactory inhibition of attack on rat pups. Ten out of 12 attack electrodes supported self-stimulation. Attack, alarm, and an oral response group were elicited from anatomically differentiated areas, supporting the hypothesis that hypothalamic motivational responses are produced by multiple overlapping substrates, and not by a single undifferentiated substrate.