The nasal valve consists of four distinct airflow-resistive components. (i) The vestibule terminates in an airflow-resistive aperture between the septum and the caudal end of the upper lateral cartilage. Its cross-sectional area is stabilized by the cartilaginous structures and by inspiratory isometric contractions of alar dilator muscles. Its walls are devoid of erectile tissues that might otherwise affect its cross-sectional area and airflow resistance. By contrast, (ii) the bony entrance to the cavum is occupied by erectile tissues of both (iii) lateral (turbinate) and (iv) septal nasal walls that modulate the cross-sectional area of the airway and airflow resistance. The body of the cavum offers little resistance to airflow. Valve constrictions induce "orifice flow" of inspiratory air as it enters the body of the cavum, disrupting laminar characteristics and thereby enhancing exchanges with the nasal mucosa of heat, water, and contaminants. Acoustic rhinometric and rhinomanometric measurements show the sites, dimensions, and resistances of the valve constrictions and indicate that it is seldom necessary to extend septal and/or turbinate surgery far beyond the piriform aperture in the treatment of nasal obstruction.