During an investigation of the role of the mediobasal hypothalamus in the regulation of renin secretion from the kidneys, we found that lesions of the ventromedial nuclei prevented the increase in plasma renin activity produced by p-chloroamphetamine. In the present study, we tested the effects of bilateral electrolytic lesions of the ventromedial nuclei on the increase in plasma renin activity produced in sham-operated rats by immobilization, head-up tilt under inactin anesthesia, and a low-sodium diet. Ventromedial lesions reduced or abolished the plasma renin activity increase to all three stimuli without any change in plasma angiotensinogen. The plasma renin concentration responses to immobilization and a low-sodium diet were also reduced. All these stimuli probably exert their effect by way of the sympathetic nervous system. The data support the hypothesis that the ventromedial nuclei or neural fibers passing through them are important in the renin response to diverse stimuli that act by way of sympathetic discharge.