This study was conducted to investigate the effects of sleep and nasal resistance on pharyngeal airflow in a group of healthy male adults without complaint of habitual snoring. Twelve subjects aged 21 to 60 years were studied in a sleep laboratory during exclusive nasal breathing. Nasal and pharyngeal airflow variables were measured concomitantly at different stages of sleep. Awake pharyngeal resistance averaged 0.02-0.03 Pa/cm3/s in recumbency. In stage 2 sleep and quiet breathing resistance increased by a factor of 3-4 and by a factor of 7-8 during snoring. Increased nasal loading did not increase pharyngeal resistance further or induce snoring. Mostly, increased pharyngeal resistances were of similar magnitude in both phases of respiration, but in a few instances inspiratory resistance exceeded that in expiration, and in a similar number the reverse was found. Overall, compliance of the pharyngeal airway was not a prominent feature in this group of subjects. The relationship between transpharyngeal pressure and resistance should be studied further in order to simplify future studies of airflow during sleep.