Simultaneous measurements of nasal airway resistance and vascular perfusion of the nasal mucosa were carried out in the dog and rat. Nasal blood flow (perfusion pressure) and nasal venous pressure (jugular venous pressure) were found to have a linear correlation with nasal airway resistance. The slope of the percentage change in nasal airway resistance to perfusion pressure was 0.03 to 0.04%/mmHg and resistance to nasal venous pressure, 1.15 to 1.28%/mmHg. The results therefore indicate that alterations in venous outflow resistance are more effective than alterations in arterial inflow in changing nasal airway resistance.