We exposed 16 healthy human volunteers to air temperatures ranging from 7 to 39 degrees C and measured nasal mucus flow, nasal airflow resistance, forced vital capacity, rectal and body surface temperature, and air temperature within the nasal passage. A moderate fall in nasal mucus flow rate in the anterior and middle parts of the nose was observed with temperature above or below 23 degrees C. The nasal airflow resistance decreased in warm air and tended to increase in cold air. No significant changes in forced vital capacities or rectal temperature were observed. Nasopharyngeal end inspiratory air temperatures at 23 degrees C averaged 32.6 degrees C. At environmental temperatures of 15 and 31 degrees C they average 28.1 and 32.8 degrees C, respectively. Although we found alterations in upper airway function associated with altered inspired air temperature, over the range of 32 degrees C studied these changes were of minor physiological significance.