Hemorrhage is usually accompanied by a considerable increase in the plasma osmolality and glucose concentration due to an augmented release of glucose from the liver. In the present cat experiments an attempt was made to investigate the possible role of different vascular receptors in mediating this hyperglycemic (hyperosmolar) response. Bilateral vagotomy or stimulation of the carotid chemoreceptors by perfusion of the carotid sinus with venous blood at normal pressure only slightly increased the arterial plasma glucose concentration. On the other hand, when the sinus nerves were cut in the vagotomized animal, thereby simulating complete unloading of the carotid baroreceptors, the arterial plasma glucose concentration rose by about 8 mM/L and the arterial plasma osmolality by about 10 mOsm/kg H2O. Perfusion of the carotid baroreceptors with arterial blood at different levels of hypotension showed that the baroreceptor-induced hyperglycemia was graded in relation to the pressure level. Regional hypotension of the liver, pancreas, intestine, kidneys or brain did not significantly affect plasma glucose concentration or osmolality. We conclude that the reflex release of glucose from the liver during hemorrhage mainly is initiated from the unloading of arterial baroreceptors.