Three measurements of small airway dimensions and a measurement of lesions in small airways were made in 32 human lungs obtained at autopsy in order to assess the intraobserver and interobserver variability of these measurements and their interrelationships. The same measurements were then made in 22 lobes resected in patients with known lung function. Small airway dimensions were smaller in surgically resected lobes compared to autopsy lungs suggesting persistence of muscle tone in the surgical specimens.