Approach and escape latencies induced by hypothalamic or central grey stimulation were measured in the rat by means of a shuttle-box technique. In order to compare the effects obtained at various brain sites, the maximal value of the escape latency/approach latency ratio was determined within a given range of stimulation intensities. The ratio was shown to have high values at sites located in the ventral part of the central grey (in or near the dorsal raphe nucleus) or in the lateral hypothalamus. It was equal to zero for most of the sites located in the dorsal part of the central grey, as the rate regularly interrupted the stimulation without initiating it again. Intermediate values were obtained at sites located in the medial hypothalamus and in the dorsal pontine tegmentum.