In the presented studies, both the spontaneous motor activity and the locomotor responses to amphetamine challenge were assessed in normotensive rats and in hypertensive rats. As compared to their appropriate controls, both experimentally (either renal or deoxycorticosterone salt) hypertensive rats and spontaneously hypertensive rats maintained a higher level of spontaneous motor activity. In addition, intraperitoneal administration of amphetamine produced stimulation of forward locomotion, and head and body rearing (as shown by an increase in gross movements) and increased grooming and sniffing (as shown by an increase in fine movements). It was also found that either experimentally or spontaneously hypertensive rats displayed a greater degree of locomotor stimulant responses to amphetamine administration as compared to their appropriate controls. The results indicate that the mechanisms underlying the pathogenesis of hypertension may be related to the development of locomotor hyperactivity in rats.