In dogs pressing a lever for a brain-stimulation reward, arterial blood pressure (ABP) was elevated for 20 out of 24 sites tested, but this effect was usually conspicuous only at twice the threshold current sustaining stable performance. Hypertension was seen only in one ventral tegmental and two hypothalamic sites. In three anterior placements the ABP and heart rate (HR) increased more upon a fixed ratio than on continuous reinforcement. In most sites, self-stimulation was accompanied by cardiac acceleration; however, in some placements the HR was similar to or even less than control values. Continuous stimulation (5-10 sec) at one nucleus accumbens and four hypothalamic sites by the experimenter was aversive and produced a clearcut pressor response. The cardiovascular changes seem to depend on a spread of current to brain centres controlling circulatory functions and also, to some extent, on the animal's motor activity. The results contradict the claim that a causal relationship exists between the autonomic concomitants of self-stimulation and the intrinsic nature of the brain-stimulation reward.