Patients suffering from allergic or vasomotor rhinitis usually show nasal mucosal hyperaemia, engorgement, hyperrhinorrhoea and obstruction of the nasal airway. The nasal mucosa is drained by two venous systems which are anatomically and functionally separate. The nasal mucosa receives tone discharges from the sympathetic nerves but not from the parasympathetic nerves. Sympathetic nerve stimulation causes constriction of the resistance vessels via the alpha-adrenergic mechanism and constriction of the capacitance vessels via the alpha-adrenergic mechanism and some non-adrenergic and non-cholinergic mechanism; the capacitance vessels are under more prominent sympathetic influence than the resistance vessels. Parasympathetic nerve stimulation causes non-cholinergic dilatation of both resistance and capacitance vessels; dilatation is more pronounced in the posterior venous system. Simultaneous optimal stimulation of the autonomic nerves resulted in vasoconstriction, especially of the capacitance vessels. Hence, nasal congestion may be related more to a withdrawal of sympathetic discharge than to an overactivity of the parasympathetic nerves.